Tepig is a new fire type pokemon in Pokemon Black and White. Tepig evolves into Pignite at level 17, which then evolves into Emboar at level 36.
Tepig is one of the three starter pokemon, and can not be caught in the wild, and neither can any of its evolutions.
If you want all three starter pokemon, you’ll need to get to the first pokemon center where you can trade pokemon. Trade your starter, then restart your game. Do this process twice picking different pokemon. On your third restart, have all of your starter pokemon traded back and you’ll have all three starter pokemon.