Backing up your WordPress site is something you should take very seriously. If your site gets hacked or you somehow get locked out, you will have no other option but to rely on your backups to get your site back up and running the way it was.
These backups can be managed and stored in various ways. You can do them manually or use an automatic service that does it for you. In turn these backups can be stored on your computer or on some other storage service such as Dropbox.