Counterparts are pokemon that share a lot of similarities and tend to be the version exclusive pokemon or have some relation to eachother, but not always. Think about Espeon and Umbreon, Lotad and Seedot, Zangoose and Seviper, Kabuto and Omanyte
There's also a lot of pokemon you might not know are counterparts! Like
Meowth and Mankey, who both evolve at the same level and are version exclusive in Kanto and Johto games
Turtinator and Drampa, who are both single staged pokemon and are version exclusive in Sun and Moon and Sword and Shield. They also share the same catch rate and base stat total
Teddiursa and Phanpy, who are both version exclusive in Johto games and share a catch rate. Both these 2 and their evos match in base stat total with eachother
