Difference between user id and character name
The user id is your login name. It is the name you use when you sign into the website and the game.
The character name is the name of your character you create under your user id. Each user id can have up to 3 characters.
If you have multiple user ids and would like to purchase an item from the item mall for one of your characters, be sure to use the correct user id that character is associated with.