Explain atonement theory like I'm five

I started reading about penal substitutionary atonement and discovered that there are several different theories about atonement and that it's actually a topic of debate between the different denominations. I wanted some more information but the theological language was kind of going over my head when I went to wikipedia. If someone smarter than me could please explain the theories in simple terms that would be great. Bonus points if you can tell me what Catholics believe since I am Catholic and I should probably know the answer to that.