An Internet Protocol version 4 (IPv4) address plus a subnet mask defines which addresses are local. The default gateway is how you leave the local network. Private ranges (10.x, 172.16–31.x, 192.168.x) sit behind Network Address Translation (NAT (Network Address Translation)) and are not reachable from the internet without a deliberate port forward or Virtual Private Network (VPN (Virtual Private Network)).
DHCP hands out addresses automatically. When a device shows an address starting 169.254, it never got a DHCP reply — the cable, port, VLAN (Virtual Local Area Network) or DHCP server is the problem, not the website the user was trying to open. Reservations pin a specific device to a specific address; static addresses are configured on the device itself and must be recorded or they will collide later.
The Domain Name System (DNS) turns names into addresses. 'I can ping 8.8.8.8 but no website loads' is a DNS failure, full stop. Check which DNS servers the client received, whether the router is forwarding correctly, and whether a filtering service is blocking the domain.
Learn the tools with intent: `ipconfig /all` (or `ifconfig`/`ipconfig getifaddr en0` on macOS) tells you address, gateway and DNS; `ping` tests reachability; `nslookup` tests resolution; `tracert`/`traceroute` shows where the path stops; `netstat` shows what a machine is actually connected to.