There are alot of diffrent things between improv and acting.The main difference is that in improv you don't have a script to read off of but in acting you do.Another thing that is different is the classes..In improv classes, you play a lot of games related to improv. And in acting classes you get a script and rehearse. Another difference is for dress rehearsals in acting,you have to have costumes and in improv,you don't have dress rehearsals,however if you have shows in improv you know when the are.These are a few differences between acting an improv.