"have done" is used in present perfect tense, while 'did' is used in simple past tense. We use present perfect tense when we want to link the present with the past, eg: through asking a question in the present regarding something you might have done in the past. "Have you done your homework?", "Yes I have done my homework" We use simple past tense when we want to talk about something done in the past at a specific time, eg: "I did my homework last night" I got no idea. ... I've got not idea? Should be - 'I have got no idea' or 'I've no idea' Hope this helps.