What is a non-manifold mesh and how to fix it

In your jour­ney through the world of CGI, you have prob­a­bly come across the word non-man­i­­fold once or twice. Maybe you got slapped with a “mesh is non-man­i­­fold” error too and won­dered how your mesh became non-some­thing. Surely hav­ing a man­i­fold mesh is bet­ter. But what does it mean to be man­i­fold? A man­i­fold is a math­e­mat­i­cal