It's used to ask confirmation and to tell something that accepted by default. Example: 성열이 너무 멋있지? (Informal) - Sungyeol is so handsome right? 성열이 너무 멋있죠? (Formal) 내일에 학교에 가야지. (Informal) - Of course I need to go to school tomorrow. 내가 최선을 다 해야죠. (Formal) - I need to do my best, of course.

Asking confirmation like "..., right?" It can be 지, 지요 (polite) - Also written just as 죠