Charizard evolves from charmeleon at level 36 and from charmeleon evolves from charmander level 18.
It is one of 21 starters at the Professor's office, or, if you're lucky, someone will trade it with you. You unlock the trade resort after the first gym. You can teach moves from TMs and HMs, like overheat (from 2nd gym), fly (from 5th gym), and substitute or baton pass (from arcande in Anthian city). It is weak to ground, rock, electric, and water and good on ice and leaf types.