"When you walk in the grass (or anywhere else), you may encounter a wild creature. Battle it, and win, and you 'get your opponent's phone number', which (I think), means that you can call it when you want it to battle for you. No Pokeballs, no choosing whether you want the thing or not, it becomes yours. Oh, and these 'electric monsters' will randomly call you up and prattle about stupid stuff. One asked if I'd eaten curry."