What is a Pokemon gym?
Gyms are specialised locations in the Pokémon GO world. They’re pretty hard to miss as they’re represented by giant towers – usually with a Pokémon at the top.
At any one time the gyms can be held by one of the three teams – red, blue or yellow. You’ll be able to tell which one from the colour and emblem on top of the tower.
The job of the team is to defend it by leaving high-level Pokémon there. If the gym is a different colour team from you, that’s when you can battle there.