It allows you to manage users and their levels of access to the AWS resources. Here are some key points to remember when thinking about IAM:

IAM is universal, it is not specific to a region or AZ

Centralized control to the AWS account

Shared Access to your AWS account

Granular Permissions

Identity federation (like Active Directory)

MFA – Multifactor Authentication – Two factor Auth

Temporary access for users

Allows you to set up your own password rotation policy

Integrates with many different AWS services and supports PCI DSS compliance