Unlocking means being able to run your own custom ROM on your phone.. ROM includes the Operating System (WM 6.1), all the programs you use, and basically everything that makes your phone run.. If you want to unlock your 6700, check out the 6700 forum..
http://forum.ppcgeeks.com/forumdisplay.php?f=14
Search and if you can't find an answer to your question, post a new thread... I do not know much about your phone... So I recommend asking people in that forum..