Port 3389 is conventionally used by the Remote Desktop Protocol (RDP) which enables users to connect to and control another computer over a network connection. Understanding port usages is crucial for network troubleshooting and security. While the other ports listed are also used for well-known services, they are associated with other protocols and services: Port 443 is used for HTTPS, port 22 is used for SSH, and port 25 is used for SMTP.