Accuracy: chance to hit an enemy when your bullet flies through their tile.
Scatter: how far your bullet can deviate from the aiming line shown to you.

I see, thank you very much. So improving scatter is actually far more important than accuracy, as that is really easy to get to 100%.

Originally posted by fudeu:

I see, thank you very much. So improving scatter is actually far more important than accuracy, as that is really easy to get to 100%.

Note that accuracy is opposed by enemy evasion, and enemies *can* have nonzero evasion - very prominently the new Drone and Dog enemies for instance, although there are also Human enemies with relatively high evasion. You will need more than 100% accuracy to guarantee a hit.

Scatter is very important because you only get an accuracy check if the bullet passes through the tile the enemy occupies - essentially a second chance to miss on each shot (though scatter has a few benefits if you are fighting large, dispersed groups of enemies and want to hit as many as possible).