Its not a terminology thing, but rather about understanding what the software you’re using is doing and against which modes of failure you’re protected against.
If you’re copying your working directory to your backup disk and that is all, then what you have is redundancy. If you accidently delete a file and then run your backup, then the file you deleted is also deleted on the backup. You are protected from your driver in your computer failing or the back up disk failing, but that is it.
If you have a good backup tool that manages point in time backups for you, you’re a lot better off than just copying to an external disk.