How To End A Level

hi guys,i am having a a very basic question,
how do we end a level in platformer type games??

 

Looks like Giana Sisters _Level Complete
I have nothing in my Games i Have Get ready next Level

 

and what if there are 3 level
and i want that at the end of level when the player touches a certain object the level is finished
and player is taken to choose world level.