What are the specific names for the syntax various of windows usernames?

What are the specific names for the syntax various of windows usernames?

When windows users are prompted to enter their username, they can usually
specify it in a variety of formats:
username
username@activedirectorydomain.example
addomain\username
What are the technical terms for each of these? I'd like to know for
future reference in case I need a specific format entered.