If you've previously used Opera, then you'd have a good idea of what mouse gestures are, however....
Mouse gestures allow you to navigate (say with K-Meleon) without the need for clicking on the navigation toolbar buttons. All you do really is right click with your mouse, hold it down, and then move the mouse left, and release the button to go back a page, or click, hold & move it right to move forward a page.
For more info, check out the StrokeIt page:
http://www.tcbnetworks.com/strokeit/