Executions are a type of finishing move in For Honor
If your final move is a heavy attack then you are given the chance to do an execution. Every character will have four unique executions, with more being added as time goes on. While they can be interrupted mid-animation, if they aren't, they will brutally finish off your opponent and make it impossible for them to be revived as well as regenerate some health and fully recharge stamina. It will also apply an additional 3 seconds to the time penalty before the felled enemy is allowed to respawn. Different executions regenerate different amounts of health depending on the length of the animation (longer ones heal more health than short ones), and the impact of execution health regen by gear.