Car Stereo: Noobified: I am confused.

[Turkish]

Alright, I was looking through the stuff that came with my car when I bought it, and I came up with all these amplifiers, crossovers, and millions of cables...
I kinda know what amplifiers are but I am not sure about crossovers? What are they? What do they do? What's the purpose of having 2 amplifiers and 2 crossovers? I am really confused. Any help will be appreciated, did I mention, I am confused!

 

[bunker]

A crossover splits the frequencies. Sends higher frequencies to tweeters and midrange speakers and low frequencies to subwoofers.