@paok1970,
paok1970 wrote:
Is there a difference in meaning between the following two questions? And when do you use them?
1) What have you done?
2) What have you been doing?
Thank you.
The second one is generally used as polite, conversation-starting inquiry. Sort of like "what have you been up to lately?" But it can also be used in less innocuous contexts.
The first one would be common when the questioner knows (or suspects) the guy has committed a highly unusual deed--perhaps something criminal or otherwise startling or dubious. In this context, "what have you been doing?" might work just as well, depending on the circumstances.