Why is my Zoom video backwards and how do I fix it?

Zoom has really taken off over the past few years, but there's one thing that always seems to catch people out. If you've come to this page, you're probably trying to understand why, when you see yourself on a Zoom call, everything you see in your Zoom video is backwards, with things like text and clothing motifs appearing the wrong way round. The same will happen in Google Meets and Microsoft Teams.