This might get a bit detailed but please stick with with me. When you got your opponents health down low, you would be able to pull off a finishing move. They wouldn't be as likely to hit, does the same damage as a normal attack, but you get some extra XP, maybe 10% or whatever would work.
Your alignment decides what you can do. For lightsiders it would be something like chopping off an arm or leg, destroying their weapon etc. Basically disabling moves. If you are darkside then there will be some more execution/humiliation moves. Like decapitation, chopping them in half., or other painful stuff.
Also, what force powers you have would determine what you could do. Like if you had saber throw you could throw them in the air, then throw your lightsaber at them. Or if you had force choke then you could hold them in the air and while they're choking, chop off their head. Or if you have Force Speed then you do a sort of really fast charge, that looks a bit blurry.