No matter what your desires are, or what your progress in Pokemon GO is, you will have — once you reach Trainer Level 5 — to battle in Gyms to proudly display your team's colors.
Although the game has little to do with the core series, the Gym system does exist. These Gyms will be available in well-known locations. You can try to take a Gym if it is not the same color as your team's or if is not affiliated (it will be gray).
When you control a Gym, you will have to choose a Pokémon that will remain there to keep it under your colors.
Pokémon Motivation
The new Gym system, which replaced the old Prestige system, uses a meter to show that Pokémon's desire to defend that Gym. This is called Motivation.
It is shown as a heart above the Pokémon's head. This heart begins full, and decreases as its Motivation falls — meaning its CP also decreases (temporarily).
Defending Gyms
In order to maintain control of the Gym for as long as possible, you can feed the Pokémon defending it Berries. This restores the Motivation of that Pokémon, meaning it can fight longer!
Feeding a Pokémon Berries nets you Stardust and XP - but note that you can only feed a Pokémon ten Berries before being subjected to a cooldown.
Capturing Gyms
In order to take a Gym from a rival team, you need to beat the Pokémon defending it.
Note that when you defeat a Pokémon, its Motivation will not decrease fully - it can take several battles to reduce to zero.
Once a Pokémon loses all its Motivation, it faints, and returns to its owner. Doing this for all Pokémon on a Gym means that Team will lose control, and it will turn gray again. Simply add a Pokémon to it then to claim it for your Team.
Gym Awards
For each Gym you own, the number on the "Shield" at the top of your screen in the Shop section will be increased.
This shield indicates the number of Gyms YOU currently own.
You can earn up to 50 PokéCoins per day for leaving Pokémon to defend a Gym.