Cobblemon is basically an emulation of Pokemon for minecraft, it adds most of, if not all of the pokemon from the nintendo games, and allows them to interact with the game in many different ways
It also adds a new mechanic to the game, rather than the ender dragon being the end, battling legendary pokemon, facing off against other players in rival battles, or even attemtping to become the proclaimed "Pokemon Mogul" from trading to obtain all the pokemon you can.
From cooking, to catching 1/8000 chance shiny pokemon, it just makes the game all around more fun