Firewall
Software or hardware that controls which network traffic is allowed in or out based on rules.
On a Linux server, ufw or nftables lets you allow only the ports you need (e.g. SSH) and deny everything else. A firewall is a core layer of a secure home server.
Related articles
SSH(Secure Shell)
An encrypted protocol for securely logging into and managing servers over a network.
Port Forwarding
A router rule that directs incoming internet traffic on a specific port to a device on your local network.
NAT(Network Address Translation)
The router technique that lets many private devices share one public IP address.