Email Address
Your email address is used as your username.
First Name
Used as a security question if you lose your password, and for displaying to others.
Middle Name
Used as a security question if you lose your password, and only the first letter is displayed to others to distinguish you from people who share the same first and last name.
Last Name
Used as a security question if you lose your password, and for displaying to others.
Gender
Used as a security question if you lose your password.
Birthdate
Used as a security question if you lose your password, and the year is hidden from others.