LUA[en.wikipedia.org] is the Source 2 scripting language. It's compiled at runtime by the game executable during the level load, and conveniently, can also be reloaded by restarting the map for quick iteration without having to recompile the map nor rebuilding VPK.

A great example of something created on Source 2 and utilizing LUA VScript is Robot Repair:

Through a mixture of Hammer and VScript, Robot Repair was created using the same tools; such an expierence could theoretically be created in Destinations.

LUA scripts are found in the maps_scripts folder for your custom content addon:
...\Steam\steamapps\common\Destinations\game\steamtours_addons\YOUR_ADDON_NAME\scripts\vscripts\map_scripts\

Note: Scripts folder structure may not exist, so you will have to make it.

The engine looks for a LUA file that has the same name as your map in the maps_scripts folder:
...\Destinations\game\steamtours_addons\YOUR_ADDON_NAME\scripts\vscripts\map_scripts\YOUR_MAP_NAME.lua

To verify the game has found your script, you can open up the VConsole and filter for "map_script" to see what's been reported:

You'll want to use an integrated development environment (IDE) to help make your scripting easier with syntax highlighting, formatting, functions, etc...

Some great options are:

• UltraEdit[www.ultraedit.com]
  
• Sublime[www.sublimetext.com]
  
• Decoda[unknownworlds.com]