Friend

Friends are other player characters that you can keep track of in the Friends List. When a Friend enters the game, you get notified as a system message, usually in yellow text. The /friend command allows one to add the target to the Friends List directly.

Other uses
For the purpose of spell targeting, friend can refer to:
 * A mob with which you have "friendly" or better reputation.
 * A player in your faction or their pet.