Some of the better class and items?

I'm fairly certain he posted in the wrong forum.

Long range physical attack certainly describes ADCs.

Certain roles work better at different elo (difficulty) levels, and items have different purposes for different situations, champions, etc. If you're just starting out, I'd say pick up Caitlyn or Ashe, and buy a Bloodthirster after you get your Berzerker Greaves.

Ultimately however, the game is made so that at a really skilled level, champions all have their uses and aren't significantly stronger than each other in their own roles. However, due to the tools and methods that they accomplish their means and ends, certain champions have certain counters, and certain champions are very good at certain things, etc.