ssh-agent

A program to hold private keys used for public key authentication

Summary

The ssh-agent is a helper program that keeps track of user's identity keys and their passphrases. The agent can then use the keys to log into other servers without having the user type in a password or passphrase again. This implements a form of single sign-on (SSO).

The SSH agent is used for SSH public key authentication. It uses SSH keys for authentication. Users can create SSH keys using the ssh-keygen command and install them on servers using the ssh-copy-id command.

Reference

ssh.com Docs

How to configure ssh-agent, agent forwarding & protocolSSH Communications Security