Minecraft wiki entry for Demo_mode, associated text: Players can play only the tutorial world. Selecting Play on the title screen takes the player directly into the tutorial.
The tutorial starts every time the player enters the world; there is no option to skip it.
Only local multiplayer works, as the world selection screen is skipped altogether.
Saving is unavailable. Users are asked to buy the full game when "Save Game" or "Exit and Save" are selected.
Texture Packs, mash-up packs, and Skins, although they can be bought, cannot be used.