1. Features

As vassal
Persuasion attempts to convince your king to start a war
Appoint a chamberlain, who will decrease tax inefficiency by 10% and gives you the ability to set tax rates. Taxes also have an effect on center relation and prosperity. In addition he will take care of paying wages and collecting income as well as giving you the possibility to secure your money
Let your companions pick items from the chamberlain item pool (autoloot)
Appoint a constable who recruits and trains troops and provides information about garrisons and troops of lords
Send patrols to important locations
Appoint a chancellor who sends gifts and messengers to other lords
Village and town riots may occure if the people hate you and have to pay high tax rates. Counter them or negotiate with the leader.
Let your spouse buy some food (I know, it has nothing to do with diplomacy but it's fun :mrgreen:)
Pay staff salary (you knew that a woman will cost money before you married her :P)
Troops will start running away if you go into debts (this also applies to garrisons)
Return fiefs to your king, he won't like this, though
Move your residence (via spouse)
Negotiate Mid-siege surrender/walk-out terms if defending your own keeps and towns
Affiliate to families
Send scouts to settlements
Pay to avoid defeat

As king
Threaten other kingdoms with war and try to squeeze money out of them
If a faction sues for peace you will have the option to set terms
Possiblity to send a gift to another faction (fief or money)
Send a spy to another kingdom
Form an alliance, conclude a defensive pact, sign a trade agreement or conclude a non-aggression treaty with another faction.
Change the domnestic policy of your kingdom. Choose between Centralization/Decentralization, Aristocracy/Plutocracy, Serfdom/Free subjects, Quality/Quantity which affects trade income, vassals armies size, AI army strength, relation between king and vassals as well as tax inefficiency
When asking for a truce you will get the option to pay and/or give fiefs to conclude a truce.
If another faction recognizes you as king you will have the option to ask for help against your enemy and in certain circumstances support the decision by paying money
Choose your faction culture so all your lords will recruit the same type of troops
Exchange or release your (own) prisoners
Distribute spoils of war after you conquered a town or castle
Send emissaries to persuade lords to join your kingdom

Misc/Technical
Mod works with native save games. (save games of older Diplomacy versions might not work, though)
Battle continuation and free death cam
Amount of recruits available in villages will depend on honour, renown, being owner, being king, domnestic policies
Horses will become slower if they are wounded
new visual presentation of faction relations
Integration of 3.3.2+ by zParsifal

Here is the link to the forum page too:
https://forums.taleworlds.com/index.php?topic=116424.0

Sorry if I wasn't specific enough in my question, but I meant the diplomacy tab that pops up when you camp. That's what was confusing me.

Here is some info off of the forums I hope this helps. If not just let me know. Thanks.

OPTIONAL ECONOMIC CHANGES (as of Diplomacy 3.32+)

This setting can be changed between OFF, LOW, MEDIUM, and HIGH/EXPERIMENTAL through the camp menu, and defaults to LOW. Each setting includes all of the changes of the previous levels.

Enabled on LOW or above:
When trade occurs between towns, the benefits are split between the buyer and the seller, instead of just the buyer. (The rationale for this is that in Native, there is no incentive to export goods.)
Merchant caravans take into account distance when deciding the most profitable trade route, as well as any mercantilistic policies imposed.
Reduce price convergence caused by NPC travelling merchants (from 30% in Native to a random percentage with an average of 15%).
Increase food prices in towns under siege.
When the player surrenders, depending on who accepted his surrender and other factors, they may not loot his personal equipment. (This is to deal with the problem that when permanent stat loss is not possible, there is no way reason to ever surrender, since you lose the same soldiers and items either way and if you fight at least you can reduce your opponent's army.)
The available gold at merchants changes with town prosperity.
You receive slightly better prices selling items to the correct merchants.
The rate of food stock replenishment for a castle depends on the prosperity of its village, and is stopped while the village is raided.

Enabled on MEDIUM or above:
When promoting a companion to a lord, modify their starting gold (which is supposed to represent their accumulated share of the loot) by their Trade and Looting skills.
When calculating player enterprise profit (both for real and estimated) don't just use the price of the raw materials, but also whether they are actually available. If there is no locally-available supply, the good will have to be imported, and the effective price depends on the prices of the town's trading partners and the frequency of caravan traffic with them.
Food consumption at both castles and towns increases with garrison size. The average starting garrison size is the baseline. Troops beyond that eat more, although the change is less important in percentage terms for towns. Food consumption at towns increases with prosperity.
If a faction is run by the player (and so no one receives the weekly bonus gold that the faction leader would normally receive), and the player is married to a lord, the player's spouse receives half of the "king bonus."
Like NPC lords, the player loses gold when his fiefs are raided. (Only gold in your treasury managed by your chamberlain can be lost this way: the gold you carry with you is exempt.)
When the player party is defeated, take into account the Looting score of the victor when calculating the gold lost by the player.
If an NPC-owned castle or garrison has more troops than a certain minimum and it lacks the wealth to pay wages, it can suffer attrition.

Enabled on HIGH:
When a lord loses gold due to a village being raided, the loss is first subtracted from uncollected taxes at the village before being applied to his personal wealth.
As kingdoms are eliminated, the "king/marshall bonus" for all the remaining kingdoms increases, so the total amount of gold given out remains constant.
If a lord has an excess of gold, he might distribute some of the extra to any of his fortresses that have low wealth (and don't have oversized garrisons).
When prisoners are "sold" from NPC-owned towns and castles, a small amount is added to the fief's wealth (unless it has an oversized garrison).
Mercenary party sizes increase with the player's level, the same way that lord party sizes increase, to make them stay relevant as the game progresses.
The higher the player's honor, the greater the honor loss from misdeeds.

OPTIONAL AI CHANGES (as of Diplomacy 4.1)

This can be changed between OFF, LOW, MEDIUM, and HIGH/EXPERIMENTAL through the camp menu, and defaults to LOW. Each setting includes all of the changes of the previous levels.

Enabled on LOW or above:
When a lord is looking for a new faction to join, he is more likely to rejoin his original faction unless that is the faction he is leaving.
When the AI picks a fief to defend from attacks, give greater priority to defending fiefs with lords than fiefs without lords.
Increased the range of circumstances in which the AI will surrender to a massively superior sieging force. Factors include among other things the personality of the leader of the defenders, how much the kingdom values the fortress, and the campaign AI difficulty setting.
If a king cannot decide who to support to receive a fief, instead of automatically defaulting to himself he will decide to who to pick (which might still be himself) according to the alternate algorithm mentioned in the MEDIUM section below.
(VARIABLE) Tweak the way that potential targets for attack are evaluated, to make retaking recently-lost fiefs more attractive. The magnitude of the change varies based on how high the AI Changes setting is.

Enabled on MEDIUM or above:
Tweak the relationship loss calculation with other lords when one lord is granted a fief, to make it slightly less unreasonable (e.g. when returning a recaptured fief to its original owner).
For kings and lords with certain personalities, when supporting lords to receive villages, changed the minimum relation a fiefless lord has to have before they will support him. (In Native, they wouldn't support a lord with relation below 0, but through dialogs kings would offer villages to players with relations as low as -5.) Fixing this removes an inconsistency, and decreases the perpetually-fiefless-lord issue.
For martially-minded lords, when choosing who to support to receive a fief, they will support the conquerer more often.
Kings use an alternate algorithm for deciding which lord would be best suited for a fief. They are more likely to award a reconquered fief to the lord who held it last; they are more likely to grant fiefs to lords that are somewhat-closeby; they take into consideration ancestral claims; and they are less likely to award every single fief to themselves because they can't think of any other candidates. Other aesthetic factors also apply.
If a lord other than a king cannot decide who to support according to the Native criteria, instead of automatically picking himself he will choose who to support (which might still be himself) according to the alternate algorithm used by kings.
(VARIABLE) Tweak the way that potential targets for attack are evaluated, to make retaking recently-lost fiefs more attractive. The magnitude of the change varies based on how high the AI Changes setting is.

Enabled on HIGH:
When a lord or the player is courting a lady, the standard for the renown bonus is adjusted based on the renown of her daddy/guardian.
(VARIABLE) Tweak the way that potential targets for attack are evaluated, to make retaking recently-lost fiefs more attractive. The magnitude of the change varies based on how high the AI Changes setting is.
Under some circumstances, NPC kings might decide to give away villages they own to fiefless lords in their faction, in order to forestall discontent.

One last question. What does the diplomacy horse speed, diplomacy battle continuation, and prejudice level impact?

As your horse gets injured in battle it will move slower.
Diplomacy battle continuation is if you die during the battle it will continue without you unless you hit TAB to get out.
I think the prejudice level has to do with playing a female character and how the NPC's treat you.

Okay, thanks for answering my questions. I'm glad you're so on top of things with this mod.

this was super helpful