Fishing
Fishing is a game mode inside Team Mode.
The goal over here is pretty simple: use bait to catch some fish, and exchange the fish for prizes on the shop.
Fishing can be pretty boring tho, so it's adviced that you use a Macro if you'd like, since it's not bannable.
One of the most important rewards from this game mode are the Sinnoh Friendship Packs, that you cannot obtain from anywhere else unless they show up on Events: