In order of understanding how geometry is displayed on your computer screen, may it be 2d or 3d, one needs to understand what math people came up with to simplify our life. Basically, every computer programme that displays some kind of geometry/object on your screen probably uses these tricks. In 3d, without this, we would still have only very simple graphics.
We shall not write tens of pages explaining how this math actually works, we shall do a visual presentation of it. All modern graphics hardware, game engines, DirectX, OpenGL already have an encoded matrix helper function. Once you understand what these are, you will simply use matrix functions in order to have the desired effect.
