In Points, the basis is that there are 1000 points floating in a 3D space, and they beat to the beat of a heartbeat when the mouse is not held. Using the first two number keys, you can manipulate the points, and you can make the points fly randomly by holding the mouse. The camera will fly around it in 3D, making a pretty smooth-looking simulation.
Circles is based around the idea of circles floating in space that will always instantly expand to fully occupy their space before hitting the edge of another circle. Each circle will do this, and draw solid lines to any circle it is in contact with, and it will also draw almost transparent lines to others that are close to within two times its radius.
Maps is just a program that takes a grayscale geographic map of the world colored with brightness by the terrain height, and then it pixelizes it into blocks that will grow taller the farther you move your mouse to the right edge of the screen, all the while zooming around it with the camera!