Is it necessary to provide user credentials in the windows authentication to submit form authentication?

it is true before you summit form authentication form
you must provide username and password because authentication mode is based on cookies where the user name and the password are stored either in a text file or the database.so when user provide user credentials(username/password)so he/she will be authentication for login page by using session variable .
there are three types of authentication mode:
1)Windows
2)Forms
3)Passport