Like if there is a difference at all, I just want to know, because I had to evolve my Eevee with a fairy-type move with high friendship, but I got a Sylveon with high Affection, I'm pretty sure. Is there at all a difference? If so, what is it?
Friendship:
It affects the evolution of certain Pokémon, the power of Return and Frustration, and the availability of a few in-game items and Ribbons. Certain events increase a Pokémon's friendship (gaining a level, walking a certain amount of steps) or decrease it (fainting, using herbal medicine). Friendship was introduced in Pokémon Yellow for the player's starter Pikachu only, and expanded to cover all Pokémon in Generation II. In Generation VI, Affection, a separate mechanic, was introduced. However, from Pokémon: Let's Go, Pikachu! and Let's Go, Eevee! onward, Affection no longer exists and friendship has all of its effects instead.
It affects the evolution of certain Pokémon, the power of Return and Frustration, and the availability of a few in-game items and Ribbons. Certain events increase a Pokémon's friendship (gaining a level, walking a certain amount of steps) or decrease it (fainting, using herbal medicine).
Friendship was introduced in Pokémon Yellow for the player's starter Pikachu only, and expanded to cover all Pokémon in Generation II.
In Generation VI, Affection, a separate mechanic, was introduced. However, from Pokémon: Let's Go, Pikachu! and Let's Go, Eevee! onward, Affection no longer exists and friendship has all of its effects instead.
Source
Affection:
...stat in the core series games that was introduced in Generation VI. The player can view the "level" of this stat in Pokémon-Amie (in Generation VI) or Pokémon Refresh (in Generation VII), where it is represented by anywhere from 0 to 5 hearts. Playing with a Pokémon in these features is also the main way for the player to increase their Pokémon's affection. Pokémon with high affection gain a number of benefits in battle. The amounts that affection increases by differ in Generation VI and Generation VII, but it is also generally limited by the other Pokémon-Amie/Pokémon Refresh stats: fullness and enjoyment. Increasing affection usually affects one of these stats as well, and when they reach their maximum or minimum, affection can no longer be increased by some methods until they are offset again.
...stat in the core series games that was introduced in Generation VI. The player can view the "level" of this stat in Pokémon-Amie (in Generation VI) or Pokémon Refresh (in Generation VII), where it is represented by anywhere from 0 to 5 hearts. Playing with a Pokémon in these features is also the main way for the player to increase their Pokémon's affection. Pokémon with high affection gain a number of benefits in battle.
The amounts that affection increases by differ in Generation VI and Generation VII, but it is also generally limited by the other Pokémon-Amie/Pokémon Refresh stats: fullness and enjoyment. Increasing affection usually affects one of these stats as well, and when they reach their maximum or minimum, affection can no longer be increased by some methods until they are offset again.
Friendship and Affection are different things, with Friendship being introduced in Yellow and Affection being introduced in Gen 6. In Gen 8, the two are combined into just Friendship. For full details on benefits, which Pokemon evolve from them, and other information, check my sources.
Hope I helped!
