Guide: Understanding AWS Organizations

AWS Organizations is a critical part of the **Amazon Web Services** (AWS) environment as it enables an AWS user to centralize and manage multiple AWS accounts within a hierarchy. It's the service that automates AWS account creation and management and simplifies billing by pooling AWS resources.

Here's why it's Important:
1. Enhances account security and simplifies new account setup.
2. It manages and governs resources more efficiently.
3. Centralized Billing: All the accounts in an organization have their charges consolidated, minimizing accounting efforts.

How it works:
By setting up an AWS Organization, the user can create accounts in the organization, invite and manage invitations to AWS accounts to join the organization, and remove accounts from the organization.
Billing, security, and even some architectural decisions can be controlled at a granular level by applying service control policies (SCPs) at different levels of the organization to set fine-grained permissions.

Exam Tips - Answering Questions on AWS Organizations:
1. Always remember SCPs are evaluated after IAM policies - they don't grant permissions; they further restrict them.
2. Understand the difference between *consolidated billing* (only about costs and billing) and *organizations* (governance, management, and control).
3. Understand that there's only one root, and it can contain multiple Organizational Units (OUs), but an OU can't contain another root. Also, remember that the root and OUs are containers for AWS accounts.