Backup is basically just making multiple copies of the same files, so that if one copy is damaged, you still have another copy (perhaps a bit antedated) to fall back to. Don't be intimidated by the term!
So anything that allows you to make another copy of the same files, i.e., the files that are important to you, will do.
It is good to keep these copies at another place physically. For example, if the files are on your hard drive, make copies some place else other than your hard drive.