What is an IP address and subnet mask? How can one assign an IP address to a PC?

An IP address is a unique label for a device on a network (e.g. 192.168.1.10). A subnet mask (e.g. 255.255.255.0) separates network part from host part, telling which PCs are in the same LAN.

Assigning IP to a PC (Windows):

1. Automatic (DHCP — common): Control Panel → Network and Sharing → Adapter → Properties → IPv4 → Obtain automatically. Router gives IP. Preferred in offices.
2. Manual (Static): Same path → Use the following IP → enter IP (192.168.1.50), Mask (255.255.255.0), Gateway (192.168.1.1), DNS (8.8.8.8). Used for servers, printers, routers.
3. Verify: cmd → ipconfig to see assigned IP; ping 192.168.1.1 to test gateway.

Static for stable devices, DHCP for staff laptops — wrong gateway/DNS is why "connected but no internet".