Sometimes the only way to learn is by talking to people and asking questions. Other things you pick up along the way. Always read books. My younger decided she wanted a horse and six months later she still doesn't know what bit her horse wears, or why.
It can seem daunting at times, but it's well worth it. Never forget to learn the parts of your horse too because, trust me, it comes in handy. I never thought it would when I started.
A good book to read (if you can find it) is Stuart Tinney's Making The Time
. A very good book from a very good rider. The first few chapters detail the tack your horse wears and when and why you should use particular bits. It's mostly cross country riding, but I read it a couple of times because it was very helpful.
Hope that helps! Good luck! =)