Alt
From Alter Aeon Wiki
An alt is a term used to refer to additional characters owned by the same real life person, in contrast to a main, which is the character the person plays primarily. The terms are abbreviations of alternate character and main character, respectively. Players may create alts so they have characters with different skill sets for experimentation or just for fun.
There is no real limit on the number of characters a person is allowed to have, however they are not allowed to play more than one of them at a time (this is known as multiplaying). The only time a player is allowed to do so is for the sole purpose of transferring a equipment between the two characters, after which one must be logged off.