Help for a newbe. Really basic

Hi, thx first of all. I need to know why this happen

A polygon is funny how it works. Even if it’s four sides on a polygon it still needs to render in triangles. The more it is bent, it will try to ‘guess’ where the line of the triangle will go. Imagine how a paper looks when it is bent.

I recommend some easy tutorials for blender on youtube, I’ve heard good things of the donut tutorial.

Ok thx for that. I will go and do some tutorials. Thx again