You can choose a Pokemon, summon them then give them commands. Pretty cool!

In terms of how it all works, the animals of the game have been replaced with wild Pokemon, which you can walk up to and capture. You can then use them in fights against other Pokemon trainers; they’ll appear in the game world and go at it until one of them faints (as you can see below).

Just like regular Pokemon! Only on your PC, and in full 3D.

You can download Pixelmon here, while there’s a good starting guide here.