What is the MobileBackups Drive

I recently purchased a new MacBook Pro. When I use Adobe Photoshop Bridge it shows a hard drive Icon for "MobileBackups". The hard drive icon does not show up in my regular Mac Finder browser. When I browse through the MobileBackups drive it shows files that I have deleted. Is this a backup system that came with my new MacBook Pro? If so how much memory does it offer?

Thanks!

Pat