So, what form can these other keys take? Apart from a password, how else can you prove it’s you?

You could have a code sent to your phone when you try to log in.

If you’ve ever had to enter a code like this, you might have been using 2FA without realising it.

It might also be a special device which plugs into your computer. Without this device, the system won’t let you in.

2FA can make an account much, much more secure. While it can take time to set up, it also makes criminals’ jobs a lot harder.