What do i need to protect an idea/product?

I've looked online and since I'm only 13, I don't really understand the difference between a patent, copyright, and trademark. The ideas are all for controlling an MP3 player with more ease, but they can also be used for other products like phones or pdas. I want to be able to sell these to a company so they can start making it, but I need them to be protected or they'll just steal the idea when I contact them. And I know this is a bit of a seperate question, but what companies are out there that can help me get a patent and will do it for free or cheap? (I'm only 13, so I'm on a bit of a budget)