Candy

Candy is a consumable, Pokémon family-related resource that can be used to strengthen Pokémon. Candy is acquired by various ways such as capturing Pokémon (3 for first evolution form, 5 for second evolution form, 10 for last evolution form), or hatching eggs (various amounts). One can double the amount of candies one gets by giving the Pokémon a Pinap Berry before catching it.

Pokémon power up
Candies are used to power up Pokémon up to level 40, which may cost from 1 to 15 pieces of candy, depending on what level certain Pokémon is.

Pokémon evolution
Candies can be also used to evolve Pokémon that are capable of evolving. Evolving a Pokemon can cost 12, 25, 50, 100, 200, or 400 pieces of candy.

Second Charged Attack unlock
Candies can be also used to unlock the second Charged Attack of Pokémon with more than one Charged Attack. Unlock cost can be 25, 50, 75, or 100 pieces of candy.

Purification
Candies are necessary to purify Shadow Pokémon left by Team GO Rocket. Purification cost can be 1, 3, 5, or 20 pieces of candy.

Types
Each evolutionary line has its own candy type. Each one represents the base form and is identified by its primary and secondary colors.

Kanto=

Candy XL
Candy XL was introduced with GO Beyond, as Pokémon can also reach level 50 like Trainer. Candy XL is unlocked after Trainer reaches level 40. It is only visible in Pokémon summary page once Trainer has obtained at least one Candy XL of that Pokémon.

Candy XL is consumed instead of regular Candy to power up Pokémon above level 40. It is also family-specific. 100 regular Candy can be converted into a single Candy XL. There are other ways to obtain Candy XL, but all of them occur randomly.
 * Catching and transferring Pokémon can give 1 to 3 Candy XL. The higher the Pokémon level, the higher chance to receive more Candy XL. Catching a stage 2 Pokémon guarantees 1 Candy XL, a stage 3 guarantees 2 Candy XL, and catching Legendary Pokémon and Mythical Pokémon give 3 Candy XL.
 * Hatching Pokémon
 * Trading Pokémon. The chance of receiving a Candy XL will increase the greater the distance between Pokémon catch locations is.
 * Walking with Buddy

Similarity, each Candy XL shares the same color combination as their regular version. An item called Rare Candy XL functions like Rare Candy.

Candy events
This list does not include bonuses in Mystery Bonus Hour.

In Kanto Celebration 2018, the number of candy received from evolution and feeding in Gyms was also doubled.

Trivia

 * Number of Candy types is equal to number of Pokémon families available currently in the game.