:: Party / Alliance ::
In FFXI and other MMORPG, when you are playing by yourself, you are called "Solo player". If you are with other players it is called "Party". You will need to form party when you encounter enemies that are hard to fight against. Forming party'll help you a lot during the game.
You are able to form a party of 6 players in FFXI. 1 leader and 5 other members.
To form your party, go to your main menu and chose "Form a Party", finish some setting, get the members and you are ready to go.
:: Alliance ::
You are able to form multiple party called "Alliance" in FFXI. Maximum of 3 parties, 18 players in 1 alliance.