Backing up your files isn't complicated. The problem is that nobody explains it in a way that actually makes sense. So here it is, as simply as we can put it.
What 'backing up' actually means: Making a second copy of your important files and keeping it somewhere separate from your computer. That's it. If your laptop dies, gets stolen, or picks up a virus — you can get everything back.
The 3-2-1 rule: Keep 3 copies of your data, on 2 different types of storage, with 1 copy somewhere off-site (like the cloud). Sounds complex, but in practice it means: your files on your laptop (copy 1), an external hard drive at home (copy 2), and a cloud backup service (copy 3).
Easiest option — cloud backup
Sign up for a cloud backup service like Backblaze (about £5/month). Install it, let it run, and forget about it. It backs up everything in the background. If the worst happens, you download your files onto your new machine.
Second option — external drive
Buy a USB external hard drive (a 1TB drive costs about £40). On Windows, search for 'Backup settings' and set it up to back up to that drive automatically. On Mac, plug in the drive and Time Machine will offer to use it.
What to definitely back up
Photos, documents, anything in your Downloads folder that you want to keep, and your browser bookmarks. Most other things (software, settings) can be reinstalled.
The most important thing
Do something. Any backup is better than no backup. If you want help setting this up, that's one of our services — we'll come to you and get it sorted for £35–£50.