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. The number of rounds in a chapter or a volume is not definite. The length of a round is also not specified and sometimes when rounds are collected into volumes two rounds may be combined to form one round.
In Chuang Yi's translations rounds are referred to as "chapters", while in VIZ Media's translations as "adventures".