Overview

Think of AWS IAM as your cloud security guard. It helps you manage who can use your AWS resources (like S3 buckets, EC2 instances, or databases) and what exactly they're allowed to do with them. Without IAM, everyone would have full access to everything – which would be like giving everyone master keys to your building!

IAM works by letting you create and manage:

Users (individual people or applications that need AWS access)
Groups (collections of users who need similar permissions)
Roles (sets of permissions that can be temporarily assumed)
Policies (documents that spell out exactly what actions are allowed)

For example, you might want developers to have full access to development resources but read-only access to production, or allow certain applications to access specific databases but nothing else. IAM makes all this possible while maintaining security.

AWS IAM is the default way to manage access to your AWS account, there is another very similar service called AWS IAM Identity Center which is a newer service that you may wish to switch to for additional functionality including SSO. As an AWS Administrator and before taking AWS Certifications it is important to understand that these are two different services but with a similar name and overlapping functionality.

Example uses

Developer Access: Give your development team permission to create and manage EC2 instances in the development environment, but only view them in production.
Application Permissions: Allow your web application to read from an S3 bucket and write to a database, but prevent it from accessing other AWS resources.
Temporary Access: Grant consultants or auditors time-limited access to specific AWS resources without creating permanent user accounts.
Cross-Account Access: Enable trusted applications or users in one AWS account to access resources in another AWS account securely.

Integration with other AWS services

IAM is deeply integrated with virtually every AWS service:

Every AWS service relies on IAM to check if a user or application has permission to perform an action.

Similar services in other clouds

Azure Role-Based Access Control (RBAC): Microsoft Azure's permission management system
Google Cloud IAM: Google Cloud's access management service

AWS IAM (Identity and Access Management)

Documents

Switching to/Enabling the AWS Identity Center