When a character is in a scene, they'll have an objective a purpose for being in the scene, say a character is walking in to buy some food in a store, but the actor of the character didn't see their objective and was just walking around, with no actual reason for being there, this would confuse the audience and make them wonder why is that character even there. Characters have an objective in each seen they are in, and if you know it you put that into your character to show what your purpose is there, for that scene.
Now next is the super objective, what the character man objective is in the whole entire show! confused? Let me explain... Say your character wants to win the heart of his/her beloved, well that's your main purpose throughout the show. But you can't just automatically get your beloved's heart? What kind of show would that be? Throughout the scene you'll have just regular objectives; like slaying a dragon for our beloved or simple as running to the store to buy her something, those little things help you reach your ... SUPER OBJECTIVE!
Knowing these is important for your character, without an objective your character can seem lost on stage, and you're not conveying what they are suppose to be doing in the scene and on stage. Even if you feel your character is insignificant, it's not! They are there for a reason!
Picture Source:
http://www.skokienet.org/node/23128Source
Here's a sight that talks about and gives examples of objectives.
http://en.wikibooks.org/wiki/Theatre_and_Acting/Objectives,_Obstacles,_Tactics
