Latin conjugation help? (Not homework)?

I'm currently taking Latin I online and am learning about the second conjugation. I know a lot of Spanish and French, and with Latin, of course, grammar is very different. I don't understand why there are 4 conjugations, and what their purposes are. Why can't there be ONE way to say "I clean" instead of four, like in other Romance languages? An explanation would be VERY helpful and appreciated! Thank you!