Does this new OS automatically backup my computer everyday? When I look at iStat, it shows a backup hard drive. I don't have it connected so I don't know what it is. It is really confusing me.
Time Machine in Lion now does something called 'local snapshots' on portable machines. In the absence of a mounted Time Machine volume, it makes a temporary backup file on your hard drive which later gets copied back to your Time Machine drive when it is mounted next. I imagine the purpose of this is to keep the Time Machine backup timeline intact even when you are not constantly connected to a backup drive.
Do a search for 'local snapshots for more information.
I have TimeMachine enabled. I also have a portable harddrive i use for time machine. But I don't know what "mobile backups" are.