the short answer
The overhead press is a standing barbell lift that drives the bar from the front of your shoulders to lockout above your head, building the delts and triceps. The single most important cue is to keep the bar path vertical: pull your chin back so the bar can travel in a straight line past your face instead of looping forward.
This article is general technique education for coaches and clients, not medical or rehab advice - form is individual and overhead positioning varies from person to person, so a form check from a qualified coach is the gold standard.