I find it hard to believe that you've "looked it up" but don't know about the science behind it. Do you not have Wikipedia on your internet?

It is one thing to have questions or even doubts about the theory. It's another thing to claim to be unaware of what the theory is, or what evidence has been offered to support it, when there are multiple excellent sources of information on the topic that are easily found and presented for a non-specialist audience.