I have a Dell - Emachines Computer
Ummm, no you don't. Dell does not make eMachines. Gateway bought eMachines, then Acer bought Gateway. Dell is a totally separate manufacturer.
Does this mean I will not be able to use my Computer again or what...
No. It means what it says,
restores the system software as it was when you purchased your computer
So, once you determine the exact make and model of your computer and are sure you have the necessary procedures understood, and the necessary disks (if required - some makers use optical disks, some use hidden partitions on the drive - assuming that has never been deleted), then if all goes well, it should take you back to when you first turned it on.
HOWEVER - a full system restore is normally a last ditch effort to fix a broken computer. A full restore sets you back months, if not years in security updates and patches and nothing is learned to prevent the problem from recurring. Perhaps if you told us why you want to take it back, we can help fix the computer instead.