When you’re multiplying CFrame with CFrame.Angles, it means you’re changing the part’s rotation.
Remember, CFrame is useful for both rotation and position.
And yes, as @Prototrode said that nicer, they are matrices.
Remember that CFrame also represents position. So it looks like you’re trying to add an angle to a position.[Vector3]
CFrames are “transformation matrices”, which is a term that comes from linear algebra.
So CFrame.new, CFrame.Angles, etc. all give you a new matrix.
Whoever invented matrices two hundred years ago decided that applying one transformation matrix to another was gonna be called “multiplication,” even though it’s not really like multiplying numbers.
If you only have time to watch one video, chapter 3 is the most important IMO. Go in knowing that CFrames are transformation matrices. The video explains what a transformation matrix is