Dear /tg/

I am a longtime player of 40k, but as of a few weeks ago, one of my close friends has decided to try out Fantasy Battles.

I know nothing of this. Teach me. What are the differences? What are the armies and what are they like? I'd just look it up, but lets face it, you guys are awesome. I'd much rather learn from you.

Feel free to suggest any army you like for any reason to be my forces. Only one thats out is Orks. My friend bought the Orks vs Dwarves battle box and is keeping the greenskins as his army.