Collections

Collections are a form of user-created content on Pokéngine. They can include Mons, Trainers, Moves, Items, and Abilities. Some Collections are connected to a playable Region in-game, but many are not. You can view all collections, including those tied to in-game regions and others, under the Data tab on the top menu: https://pokengine.org/mons
Collections were formerly called Dexes; however, they have since been modified to include more than just mons but also Trainers and other types of content. 
Certified Collections are collections of Mons which have been recognized as having a particularly high quality and level of completeness.
Anyone can apply for a collection by filling out the Application form. Collections of Mons do not need to be tied to a playable Region in-game; however, each playable Region has its own Collection.