premotor cortex
The premotor cortex is a strip of the brain sitting just in front of the part that actually fires off your muscles, and you can think of it as a stage manager rather than the actor: it does not throw the punch or grab the cup itself, but it decides which movement should happen, how it should be shaped, and gets everything cued up and ready a fraction of a second before the body moves. It lives in the frontal lobe, the region behind your forehead, tucked right beside the primary motor cortex, which is the area that sends the final go signal down to the muscles.
What makes the premotor cortex special is how much it leans on the outside world. It is especially busy when a movement is guided by something you see, hear, or are told to do, rather than something you decide to do entirely on your own, in other words movements that are externally cued. A traffic light turns green and your foot finds the pedal; an arrow points left and your hand reaches that way; a coach says go and you start running. In each case the premotor cortex takes in that signal, picks the matching action from your repertoire, and prepares the muscles before the primary motor cortex finally pulls the trigger. It also helps when you have to reach around an obstacle or shape your grip to fit an oddly shaped object, because the right movement depends on what is in front of you.
Because it handles preparation rather than the raw command, damage to the premotor cortex usually does not leave a person fully paralyzed, the muscles still work. Instead movements become clumsy, poorly aimed, or hard to start when a cue is present, and people may struggle to fit the right action to the situation, a sign of how much of skilled movement is really about planning the next step rather than just contracting a muscle.
It works hand in hand with the supplementary motor area nearby, which tends to handle movements you generate from within, while the premotor cortex leans toward movements triggered by outside cues.