Port 22 is conventionally associated with Secure Shell remote administration.
The Internet Assigned Numbers Authority assigns well-known service ports, and SSH is registered on TCP port 22. Administrators commonly connect to that port when logging into a Unix, Linux, or other networked system securely.
A port number alone does not make a service secure. SSH can be configured to listen on a different port, and a service running on port 22 still needs strong authentication, timely updates, and appropriate access controls. Changing the port may reduce automated scanning noise, but it is not a substitute for real security.
Port 22 is often confused with neighboring legacy services. FTP control commonly uses port 21, Telnet uses port 23, and SMTP commonly uses port 25.