Excuse me is the polite phrase for getting attention or asking to pass through a crowd. Two words that open almost any interaction with a stranger.
It does several jobs at once. It gets attention, as in excuse me, is this seat free. It asks for room in a crowded space. It apologises for a small interruption or for leaving the table. And said with a rising tone it becomes a challenge, since excuse me can mean I beg your pardon, you cannot be serious. American English also uses it where British English says pardon after a sneeze.