OS X Lion and Mountain Lion, with Time Machine turned on, make "local snapshots" in the internal hard disk > http://pondini.org/TM/30.html
When your hard disk gets full, Time Machine will delete local snapshots, so you don't have to worry about it. However, if you want, you can turn them off or delete them, even if you don't need it
Have a look at these 2 links...
Local Snapshots Laptops
More Info here...