Data loss is a horrible thing. Unfortunately most users don’t realize they need a back until they do something that results in data loss. When they ask other users or Apple for help, the first response is usually to restore from backup. This is when they realize they should have been backing up thier data in the first place. There are three levels of backups anyone should do and the you can decide if you should do one, two or all three based upon the importance and urgency of your data.
Online file sync
There are a lot of services that offer basic free file sync. Google drive, OneDrive, iCloud drive are three of the most prominent. They all provide free storage and sync files as and when they are updated. The only limitation here is that in some cases they cannot backup files if those files need to be open. Outlook files and Lightroom for example are known to have issues.
Online backup
This refers to services like Backblaze that charge a single monthly fee and then allow you to backup any and all files. It automatically excludes OS files to prevent any unnecessary uploads. This is useful if you have need to backup a lot of data, even in the terabytes. Restoration will only be as fast your internet connection allows.
Time machine
This is a backup of your entire computer, usually with different restore points. One of the benefits of this approach over the others is that this restores everything. If your computer crashes and you get a new one, you can simply restore from a time machine backup when you first setup.