A vented kite is one that has screen material (or "empty" space) instead of sailcloth for part of the sail. The vents let air pass through the sail, so that the kite pulls less than a "full" or standard sail when the wind increases. Vented kites are not for experts - they are for higher wind conditions, and they are very nice to fly because they smoooth out a lot of the variances / gusts in the wind. This is an excellent site I love it! For Revs, there are several different levels of venting available - including "mid" vent, "full" vent, and "extra" vented, in addition to the Masterpiece mesh kites from the Shooks..
Here's a link to a picture of my "full" vented - which is my favorite kite when the wind is right. Some day I hope I'll own a an extra vent too . . .
Thanks a lot for your tips and the link. I found them very helpful!