Please go and check the official documentation by AWS for deep understanding. This is easy going or just a quick walk-through of what I learned and how to setup things quickly. 1. What is this ssm agent? This agent is basically a gateway or a back door for you to access or run commands in a server without doing a RDP or SSH or through some bastion host. Its a next level thing which provides a additional layer of security by not giving somebody direct access to the underlying server.
Technology blog to get an insight of what is going around.