Party

A party or team is a group of up to six Pokémon that a Trainer carries with them on their journey. They are only allow to have at least six member in the party.

Trainers may have any Pokémon in their party, and newly caught Pokémon will automatically fill empty slots in the party. After this team of six is filled, newly-acquired Pokémon are sent to a PC to be stored as they are only allowed to have six members with them while the others are kept in storage. If a Trainer wishes to change Pokémon into or out of the party, they can; however, must travel to a Pokémon Center or another PC-enabled place and use its Pokémon Storage System to do so. In Generation VII, Trainers can have the option of replacing their party Pokémon with a newly caught Pokémon without having to use a PC. Instead, they can now use a Pokémon box to replace members in their party as they wish.

Games
When entering a Battle, the first Pokémon in the party list is the one that will be drawn first. If the first Pokémon has already fainted then the other Pokémon that has not fainted will take their place in battle. For Double Battles, the first two Pokémon in the party list are the ones that will be drawn first by the Trainer. If the first two Pokémon are already been defeated then the other Pokémon that has not fainted will take their place in battle. Likewise, the first three Pokémon in the party will be sent out first when entering a Triple Battle or Rotation Battle. If the first three Pokémon halve already fainted then the other Pokémon that has not fainted will take their place in battle. If there are not enough conscious Pokémon to battle, then the player will simply be unable to participate in the battle. If all of the Pokémon in the party are defeated in battle, then they must be taken to a Pokémon Center and recover before the player continues their journey. During a battle, Trainers can switch the participating Pokémon with another in the party when one of the opponent's Pokémon are defeated or switch out when facing them.

Anime
In the anime, Trainers can only carry six Pokémon at a time just like in the games. When a Trainer catches a new Pokémon while having a full party, the new Pokémon cannot be used until the Trainer switches it with a Pokémon currently in the party. The Poké Ball of the newly caught Pokémon teleported away, or simply shrunk and locked itself with a red light.

Unlike in the games, it is possible for Trainers to carry an Egg while they have a full party of six Pokémon with them. This was seen in the original series when Ash traveled with his Larvitar while he had a full party already.

Official battles between Trainers usually involve each person using the same number of Pokémon. For example, most Gym battles require both the Gym Leader and the challenger to use the same number of Pokémon. There is also a battle variation known as a Full Battle, in which both Trainers are required to use all six Pokémon. In the Pokémon League Conferences, trainers to use six Pokémon during the competition. In Pokémon Showcases, Performers are allowed to use up to six Pokémon while delivering a Freestyle Performance, although this was never shown.