For Pokémon Go, Niantic introduces a new Mega Evolution feature that brings to the game stronger established forms of pokémon. Mega Evolution has been added to the Pokémon X and Y mainline series and continues in Sun and Moon, but is not included in the most recent Sword and Shield games with a similar characterisation, Dynamax.
The new resource Mega Energy, which is generated from fighting Super evolved Pokemon at raids, is used in Pokémon Go, Super Evolution. If you have enough resources, you can grow Mega Evolve pokemon, including Beedrill, Blastoise, Charizard and Venusaur.
In its new forms, Mega Evolution will have big consequences for high-level play. The pokémon will get far more powerful.
A Megabyte pokémon that potentially represents a node to the transient existence of the impact in the mainline sequence may be carried at once. You will keep track of what pokémon you had in the past, with a new Pokédex functionalities. If you've created a certain Pokémon once in a while, it will not take you as much time in the future to do it again.
Niantic will host multiple events in Sept with Major Evolutions, and a more special study quest will also take place. But when the function starts to roll out is not entirely clear.