in every game mode there are little tasks like; complete 2 games in a row without hitting bombs, slice 200 watermelons, critical hit 15 coconuts.. etc etc.
after completing one, a new one is added so you're never out of tasks to do.
just complete them you get a star for on your bandana. for level 0-10 3 stars are required to go up a level so complete a total of 30 tasks get you the level 10 belt *credit goes to: AB0N1MAT10N for giving the correct task requirements*
have fun slicing!