Collection Challenges are events that require the player to obtain a pre-set collection of Pokemon during the event window. In general, the goal is to actually catch the Pokemon, meaning trading/evolving will not check them off on the list. Completing these challenges generally rewards a special medal and a special set of items.
List of Past Collection Challenges
Go Tour: Kanto
January 20, 2021 - TBA
All Pokemon with the national DEX number of 1-150
This Collection Challenge also allows for Evolution and Trades to count towards the total.