A LAN (local area network) is everything behind your router talking to each other at home. Once you can picture IP addresses, DHCP, DNS, and NAT, local URLs and “why can’t my phone see my server?” start to make sense.
Every device needs an address so packets know where to go. On a typical home LAN you will see private addresses like 192.168.0.50 or 10.0.0.12. Those are reusable ranges defined for internal networks; they are not globally unique on the public internet.
Your router usually has one private address facing the LAN (often 192.168.1.1) and a public address on the WAN side from your ISP. Devices on Wi‑Fi or Ethernet get their own private IPs on the LAN.
DHCP (Dynamic Host Configuration Protocol) is how most routers hand out IP addresses automatically when a laptop or phone joins Wi‑Fi. The lease can change after a reboot unless you set a reservation (static DHCP) for your server’s MAC address — a good habit so bookmarks to http://192.168.x.x keep working.
Default gateway is the router’s LAN IP: your devices send traffic “off this subnet” through that hop. No gateway → no path to the internet.
Humans use example.com; computers use IP addresses. DNS is the distributed phone book that maps names to addresses. Your router often acts as a DNS forwarder to your ISP or to resolvers like Cloudflare (1.1.1.1) or Google (8.8.8.8).
For a local-only service, you might use a .local name (mDNS/Bonjour) or a friendly hostname your router resolves on the LAN — no need to edit system files for the Coffee story; homelab guides go deeper when you self-host many services.
NAT (Network Address Translation) lets many private devices share one public IP. Outbound connections “just work”; inbound connections from the internet to a service on your LAN need explicit port forwarding (or UPnP, which many homelabbers disable for safety).
Module 5 covers security; for now, the takeaway is: LAN services are easy to reach at home; exposing them to the world is a deliberate choice.
Opening Coffee Home as local HTML files uses the file:// scheme — no web server, no LAN IP. Some embedded apps behave differently than when the same pages load over http://localhost or from another machine on the LAN (Coffee Pro’s bundled server is that second mode). The lesson is the same idea big home dashboards use: pages + a reachable HTTP origin unlock features plain file open cannot.