Size limited demo, generally 256 bytes, 512 bytes, 1k or 4k. By convention, a 4k intro must include the 128 bytes header. No matter about the length of the demo or the number of effects.
Main screen, generally showing us a lot of different things at the same time. The screen may evolve, but the basic design stays the same.
A Demo is a succession of different screens and effects without any intervention of the viewer (no spacebar pushing to go to the next part) nor disc access during the show. A Trackmo is the same but includes disc access during the show with a music played at the same time.
Collection of Intros and Demos packed on the same disc, sometimes accessible from a menu or one after the other. The viewer must use his keyboard to select parts.