what is the difference between the following two sentences?
1. Lets windup the meeting
2. Lets conclude the meeting
Please explain it in detail.
I see two differences: formality and meaning.
wind up refers more to a process (which may start quite a while before the actual end): Come on, we've only got the room for another ten minutes. I think we should start winding up this dicussion.
It's also less formal than conclude. This happens quite often - informally, people start using more expressive words, richer in meaning than what's available in a more formal register. It takes a while, though, for the less formal word to become more generally acceptable.
There are also other meanings of both 'wind up' and 'conclude': I conclude that he was winding me up. [I draw the inference that he was trying make me upset/worried/annoyed for his own amusement and for the amusement of others 'in the know'.] I assume you're not asking about these meanings, which are totally distinct.