The preseason leagues -- namely, the Great League, the Ultra League and the Master League -- will allow Niantic to observe how people are playing and make adjustments for the first season of competitive play. It could help the company determine the ideal season length and rating threshold for ranks, among other things.

To be able to play in the leagues, you'll have to walk five kilometers to earn your entry and unlock five online matches. You can do that three times a day, if you want to battle as many trainers as possible and don't mind the exercise. However, you can also use your PokéCoins to pay your way in via the Battle Now feature if you can't complete a five kilometer walk. The farther you are to the goal, the higher the price is. You'll also be able to encounter Pikachu Libre, a type of Pikachu that wears a lucha libre costume, when you play in the Go Battle League.

Niantic says it will provide updates as soon as it's able regarding the feature's rollout, so you may want to keep an eye on Pokémon Go's social media channels for future announcements.