'ssh-agent' is a program that used together with OpenSSH or similar SSH programs provides a secure way of storing the private key. Man Page https://www.freebsd.org/cgi/man.cgi?query=ssh-agent&apropos=0&sektion=0&manpath=FreeBSD+13.1-RELEASE+and+Ports&arch=default&format=html
A password-based authentication process (in the common example of OpenSSH) may be vulnerable to brute-force attacks, if no mechanism is in place to detect them. To mitigate this lack of security, ssh supports public key authentication.
In order to log in securely to a remote system via a secure shell, a private key/public key pair is generated. The private key is stored on the local machine. The public key is stored on the target machine in the $HOME/.ssh/authorized_keys file. Public keys are not sensitive information and may be known to anybody, whereas the private key needs to be protected very carefully by a strong passphrase.
ssh-agent remembers the decrypted private key so that the user does not need to type it every time he or she wants to connect or send data to the server.
Source: Wikipedia (ssh-agent)
