An IAM user is an entity that you create in AWS. It represents the person or service that uses the IAM user to interact with AWS.
You can create 5 users at a time.
An IAM user can represent an actual person or an application that requires AWS access to perform actions on AWS resources.
The primary use for IAM users is to give people the ability to Sign-in into the AWS Management Console for interactive tasks and to make programmatic requests to AWS Services using the API or CLI.
For any user, you can assign them the following:-
A username and password to access the AWS Console.
An access Key ID and Secret Key that they can use for programmatic access.
The Newly created IAM users have no password and no access key you need to create the user password.
Each IAM user is associated with one and only one AWS account.
Users are defined within your account, so users do not have to do payments. Bill would be paid by the Parent account.