A group is a collection of player characters temporarily banding together. There are two types of groups: parties and raids. The default shortcut for the party/raid interface is shift + R.
Party[]
A party is a simple group of up to five players. The party system allows players to communicate via a private party chat channel, share completion of quest objectives, and make use of an automated system to divide up items dropped by enemies.
Raid[]
A raid is a group consisting of one or more parties. It provides all the same features as a party for a large number of players working together with the benefit of being able to organize players into smaller groups to accomplish multiple tasks.