Biography is one of the key features of the Profiling system in which allows the users to freely change the bio in their profile with no restrictions over what the bio mentions or says.
The bio will be empty at the very start of your profile and can be freely changed to anything you desire from an emoji to simple greetings by using the simple command
profile bio [bio] with a total limitation of 250 characters.
profile bio I am your one and only.
The limitation is there to prevent users from exploiting the profile system to spam messages and flood the chat.