At least 2 players are required to form a party, and it can be managed by inviting and kicking out members or leaving the party.
Sending an Invite
Send your friends an invite via the Party menu in game.
Menu > Community > Party
A list of potential party members will be displayed here.
The Party menu contains a variety of options that allow players to find other players in-game. You can use the settings menu to select various parameters before initiating a search. You could also quickly find players nearby via the recommended button.
EXP and Gold from killing monsters are distributed among party members.
Dropped items are distributed in order.