An actual backup, would be a copy of said photos and vidoes on:

- An external Drive. (which is only connected to copy files)

- An external cloud service.

- Another computer that you have.

You should probably do a couple of these.

I personally backup home computers (using borg) to a home server, that server has a 2.5 2TB external HDD connected to it (2 other 2.5 external drives are kept outside of the house). A backup of important files from the nas (including the computer backups) gets copied over to the external drive nightly. Weekly the drives gets rotated.

The really important stuff is also backed up offsite on a daily basis.

My general rule is that there are at least 3 copies in different physical locations, at least 2 of which are not within "tornado distance" of each other.

The way to think about backup and DR is "what would it take to destroy all of this?" and keep making the answer more and more extreme until it is so horrible that if it actually happens you won't care about what you lost.

PS: Also always remember that a backup you don't test isn't actually a backup.

Basically like others said, there's some kind of physical separation. That way if the machine were to explode or you loose too many drives in the array you still have a copy of them. RAID protects you from a hardware failure (to some extent), a backup protects you from hardware failure, software failure, and human failure (or it should anyway). The idea is that if the cannonical version of things gets destroyed somehow the backup is available to rebuild, so it can't be alive in the same machine as the cannonical one (except maybe when doing the backup itself).

The other "rule" that many people follow is 2 is 1 and 1 is none. The idea is that anything that isn't backed up isn't protected and can't be relied upon to exist.

A cloud service like backblaze, google drive, amazon cloud drive, etc. is a good secondary backup for a lot of people even if it'll take you a month or two to get your data there to begin with.