From Bulbapedia, the community-driven Pokémon encyclopedia.
A round is the Pokémon Adventures equivalent of the Pokémon anime's episode. Rounds divide the chapter and volumes into sections, which have a separate plot, or continue the events of the last round. In the Japanese tankōbon, each round is named after the Pokémon encountered in that certain round, such as VS. Pokémon. In the English translations, the rounds are titled after puns or the same as the Japanese title. Rounds are also added up into volumes; there are times when two rounds in the serialization are combined into one in the volume release.
In Chuang Yi's translations rounds are referred to as "chapters", while in Viz Media's translations as "adventures".