Party
A party is a group of players. Players can form a party to tackle many group activities, including instanced duties such as 
Dungeons, 
Trials, and 
Raids, as well as open world activities like 
FATEs and 
Treasure Hunts. Players can use the 
Duty Finder to automatically form parties across the servers for almost all 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 consists of 4-7 players, with 4 being the most common. A 4-player light party typically consists of 1 
Tank / 1 
Healer / 2 
DPS. Nearly all Dungeons, 
Guildhests, and low level Trials are designed for a 4-player light party.
Light parties allow usage of up to level 2 limit breaks.
PvP
The current light party content is 
Crystalline Conflict, consisting of two teams of 5 players each.
Full Party
A full party consists of 8 players, typically 2 Tanks / 2 Healers / 4 DPS. Most raids along with nearly all level 50+ Trials are designed for a full party.
Full parties allow usage of up to level 3 limit breaks.
Historical
Prior to Patch 1.17, the maximum party size was 15 for a "Full Party," but there were no instanced duties at the time and very little reason to form a party at all. Behests allowed the 15-player 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 DPS. Alliance Raids are the primary content for this party type.
Chaotic Alliance Raids are instead designed for the regular full party composition of 2 Tank / 2 Healers / 4 DPS per party.
Some large-scale 
field operation raids allow for an alliance of 6 full parties, or 48 players total. This option can be seen in the Party Finder UI, but once inside the instance, the alliance UI will not be displayed.
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".
Party Members
The Party Members window may be found in the Party Menu. It is a tab of the Social window. It contains the following information:
- Current Online Status icon
- Player name
- Search Comment
- Class or Job
- Current location
- Free Company (left blank in duties)
- Languages available and the current client language the party member is using (indicated by an underline).
Opening the subcommand menu on a party member's name (right-clicking on a name using mouse/keyboard) will allow one to view their Adventurer Plate, view their Search Info, or to initiate a Vote Dismiss on them. Opening the subcommand menu on your name will allow you to edit your Search Info and set your Search Comment.
The active Party Bonus is indicated at the bottom of the window. This is a bonus to all Attributes varying from 1% to 5% according to the diversity of roles in the current party. For example, a party with a PLD, WHM, BLM, and PCT will gain a bonus of 3% - one for Tank, one for Healer, and one for Magical Ranged.
Tools
Others
Notes
- ↑ From a game mechanics standpoint, a party of 4 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.