There are now 2 game modes which are Survival and Parkour.
Survival: In this game mode you try to survive in the biocubes. You need to find nether stars to unlock different biocubes so you can get more resources. The more resources you have, the better chance you have to defeat the enderdragon.
Parkour: In this mode, you try to get to the end of the parkour. Not to complicated but gets harder as your progress.