Creating an AWS account also creates a root user. The email and password supplied at the time of creating the AWS account becomes the username and password for the root user. This combination of an email address and password is called the root account credentials.
The root account, that is, the root user, has complete, unrestricted access to all resources, including billing information on the account. This is a supreme user and its permission cannot be altered by any other user on the account.
Since the root account has unrestricted access to all the resources on the account, it is highly recommended that you avoid using the root account for day-to-day activities. On a newly created AWS account, it is recommended that you create individual IAM users based on the organizational need and assign them the required permissions. These non-root-user accounts should be used for day-to-day activities.