A sprite is a 2D image created from a bitmap file and the S4P library supports creating, moving, resizing and rotating sprites. In addition S4P supports sprite image animation and pixel level transparency (see the ghost example). A sprite's movement can be defined in terms of speed, acceleration and direction leaving S4P to take care of the movement for you. Once moving then sprites can collide - S4P has 4 collision detection modes of varying speed and accuracy.
S4P considers all sprites created move inside a single infinite 2D space called the world and the user can set the boundaries of the world to display and then zoom in and out of the display. (try out the showcase example)