The climax of your story is about intensity and proving how far your character has come. You build the intensity before the climax by continually upping the stakes for your character. The climactic moment is where the main conflict of your story is resolved. This is the point where you provide your protagonist with the most difficult barriers they have ever faced. It's also the point where your character's arc comes to its conclusion in either a positive or a negative way. This all lies in the choice between their want and their need.