width and height are built-in int variables that describe the size of the sketch.

mouseX and mouseY are built-in int variables that describe the location of the mouse.

You can use translate() to move the origin within the sketch.

You can use scale() to make the coordinate system change in size with respect to the viewport. (The viewport is the window you see on your screen. The viewport’s size is set with size().)

A function can take parameters (also known as arguments). See example ParamsFace.