Systems Manager

AWS Systems Manager is the fleet-management layer for EC2 instances, on-premises servers and edge devices. Everything it does depends on one component — the SSM Agent — and once that agent is running and the instance has the right IAM role, the whole toolset becomes available: interactive shells without open ports, remote command execution, patching, inventory, configuration state and parameter storage.

AWS Systems Manager covers the agent, the four categories of tools, and the ones worth knowing first: Session Manager, Run Command, Patch Manager, Automation and Parameter Store.

For Parameter Store itself — tiers, encryption and how it compares with Secrets Manager — the canonical page is Parameter Store.