The most common evolution methods:

Upgrade evolution, which will evolve when you reach a certain level range. In addition, there are upgrade evolutions that need to meet certain conditions, such as in a certain level. You will evolve by upgrading your location or learning a certain skill;

Evolution stone evolution, the most representative one is the Eevee family;

Communication evolution, communicate with other players to exchange Pokémon Evolve after the dream, and also carry specific props to communicate and evolve.

By the way, evolution usually refers to irreversible changes. Reversible changes such as form switching, Mega evolution or Gigantamax are not evolution.