This category lists several tens of skills and gadgets. The characteristic that makes them stand out is that all of the actions are available from the very beginning of the game. You do not need to purchase anything here, or even get promoted, in the single player mode, to unlock them.
I strongly recommend that you have a look at the entire list after you start the game for the first time, even if you are well versed in the previous installments. Also, try to remember the button mapping for those of the actions that can be activated only when the player wants them to, and not only when required by the game. For example, you do not need to strive for remembering which button is for interrogating a bandit, because the game always displays this kind of information on the screen.