I'ma just paste the description from the mod site:
LibMouseGestures is a library for tracking and using mouse gestures through a transparent overlay frame. LibMouseGestures can be used for a lot of things, including:
Capturing gestures from a frame (lines in any direction or circular movements)
Capturing gestures without locking player movement
Selecting a range on the screen (think unit selection in Warcraft 1/2/3, StarCraft or C&C)
Update:
If you want to try out how LibMouseGestures work, you can download the library as a stand-alone addon and use /mgtest to capture a single mouse gesture and have the results displayed to you.
Project is here: http://www.wowace.com/addons/libmousegestures-1-0/
API doc is here: http://www.wowace.com/addons/libmousegestures-1-0/pages/lib-mouse-gestures-1-0-api/
Update:
If you want to try out how LibMouseGestures work, you can download the library as a stand-alone addon and use /mgtest to capture a single mouse gesture and have the results displayed to you.
So liek...discuss and stuff.