Fly confusion!

[avidrise]

Hello out there, this is my first post and will probably sound quite dumb but I would rather ask than not. I just started to fly fish and am blessed to have a wonderful friend thats helping me along. We have gone twice now, long story short I am a little confused on how to pick what fly. Nymph and what nymph, Dry fly and what Dry fly, Atractor and what Atractor. Is an atractor imitating a fly or soley just a pattern that presents a color pattern that will entice a fish to bite. Any advice on the Fly part of fishing would be greatly appreciated. Thank you