An IAM user is an entity that represents a person or service. Users can be assigned an
access key ID and secret access key for programmatic access to the AWS API, CLI, SDK, and
other development tools and a password for access to the management console
Key pairs are used with Amazon EC2 as a method of using public key encryption to securely
access EC2 instances
You cannot assign an IAM user with a password for logging into a Linux instance
You cannot assign an SSL/TLS certificate to a user