I used it a couple of years ago just to try it. MS NetMeeting must be installed and configured on your machine and anyone else's you wish to invite.
When working correctly, you set up a meeting right from within SolidWorks. A meeting request goes out to whomever you've invited, internal or external if you have a good outside connection. When they join the meeting, your session of SolidWorks appears on their screen along with a dialog box on the side for chatting. In close to real time, you can rotate your model and do whatever you wish, and your guests can comment back. You can also hand over control of your session to anyone else.
It was a little jerky when I tried it but I could see where it could be usefull. IMHO it is more convenient to use a phone if possible instead of the comment box. If you've ever participated in one of SolidWorks's web-casts, the experience is similar.