AWS Identity and Access Management (IAM) is a Web service that can help you securely control access to AWS resources. You can use the IAM control over which users to authenticate (login) and authorization (with permissions) to use resources.
When you first create AWS account, originally used for all accounts is an AWS services and resources in a single point of full access to the login identity. This identity AWS account called root , only the root user is used to create the first user IAM best practices.
IAM features:
1. shared access AWS account (no need to share passwords and keys)
2. Fine authority
3. Amazon EC2 application security access to AWS resources
4. free. IAM itself is free of charge, while access to other services with IAM, collect fees for other services