Can you explain to me what FRotationMatrix is?

Hello,

Noob, here. I’m trying to understand what an FRotationMatrix does. It’s used to get the forward vector in a Move() function.

const FVector ForwardDirection = FRotationMatrix(YawRotation).GetUnitAxis(EAxis::X);

I want to understand what’s going on here. My brain is fixated on it and I’ve resorted to watching lots of maths videos for two nights. Help!