The Bible is also pretty fuzzy about why Jesus died, but that is probably above your head theologically.
Jesus died to retain God's justice, and yet show his love at the same time. You can do either one, but not both, without Jesus' death.
1) God could simply be just, and just kill us all for the sin that we deserve. That would be simple, but it would kind of be a fix for all of us, and it would mean that God didn't love us. So that doesn't work.
2) God could just save us all and, as Outi said, our sin wouldn't matter, but then he would not be just. He would let criminals get away with their sin. That would contradict his just nature.
So, to fulfill both, Jesus died FOR us, so that the price was paid, meaning that justice was upheld, and yet he still loves us, because he does not punish us for our sin.
Compare it to a court room... somebody stole a wallet, he's caught, so he has to pay $1,000. The judge steps down, takes out his wallet, and hands over the $1,000. He paid the fine, because the criminal was his son. He couldn't just say, "Son, I love you, so I'm going to let you get away with this crime", and yet because of his love, he didn't want his son to pay the price (suppose the son was broke). So, he upheld the law, but he showed his love for his son at the same time.
I may only be 16, but please don't say that things are "Over my head theologically", unless you know that for a fact.