Party
A party is a group of players. Players can form a party to tackle many group activities such as 
Dungeons, 
Trials, 
FATEs, 
Guildhests, 
Treasure Hunts and certain 
quests. Players can use the 
Duty Finder to automatically form parties across the servers for many duties. Additionally, players can use the Party Finder to form parties with specific goals by filtering players with certain requirements.
A Light Party usually[1] consists of 4 players while a Full Party consists of 8 players. An alliance consists of 3 full parties or 24 players.
Types of Parties
Light Party
A Light Party consist of 4 players, typically 1 
Tank / 1 
Healer / 2 
DPS. Nearly all of the Dungeons, Guildhests, and low level Trials are designed for a light party.
PvP
The current Light Party content is 
Crystalline Conflict, consisting of two teams of 5 players each.
Full Party
A Full Party consist of 8 players, typically 2 Tanks / 2 Healers / 4 DPSes. 
Normal Raids along with all the endgame Trials are designed for a full party.
Alliance
Alliances consist of 3 full parties of 24 players. The role mix is different for alliances:[2] three separate Full Parties of 1 Tank / 2 Healers / 5 DPSes. Alliance Raids are the primary content for this party type.
PvP
Alliance role mixes are not enforced in PvP.
- Frontline is the primary alliance raid PvP content, consisting of three teams of 24 players (3 Full Parties per team).
- Rival Wings refers to its twelve (six for each team) Light Party-sized team units as "Alliances".
Tools
Others
Notes
- ↑ From a game mechanics standpoint, a party of 2 to 7 players is considered a "light party", though almost all light party content is designed and balanced for 4 players.
- ↑ As of at least Patch 2.3 and the release of Syrcus Tower. When The Labyrinth of the Ancients was added in Patch 2.1, it used the same Full Party composition as other duties.