What is the difference between an IP address, a subnet mask, a gateway and DNS?

• IP address — the device's identity on the network, such as 192.168.1.50. IPv4 is 32 bits; IPv6 is 128 bits and exists because IPv4 addresses ran out.
• Subnet mask — divides the address into a network portion and a host portion. With 255.255.255.0 (or /24), the first three octets identify the network. This is how a device decides whether a destination is local — deliverable directly — or remote and must go via the router.
• Default gateway — the router's address, where traffic destined for other networks is sent. Without it a device can reach its own subnet but nothing beyond, which presents as "local network works, internet does not".
• DNS server — resolves names to addresses. Without working DNS almost everything appears broken even though connectivity is fine — the classic symptom is that a site fails by name but works by IP.

Private ranges — 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 — are not routable on the internet, which is why NAT translates them to a public address at the router.

Note: A 169.254.x.x address is worth recognising instantly. It is APIPA, self-assigned when the device could not reach a DHCP server — so the problem is DHCP or physical connectivity, not the device's configuration.