A network connects computers to share resources. Types: LAN (local), WAN (wide), MAN.
The OSI model has 7 layers: Physical, Data Link, Network, Transport, Session, Presentation, Application.
TCP/IP is the practical model used on the internet: Link, Internet, Transport, Application.
IPv4 uses 32-bit addresses (e.g., 192.168.1.1). IPv6 uses 128-bit for more addresses.
HTTP (web), FTP (file transfer), SMTP (email), TCP (reliable), UDP (fast but unreliable).
Switches connect devices in a LAN. Routers connect different networks and route packets.
Wi-Fi uses radio waves. Standards: 802.11ac, 802.11ax (Wi-Fi 6).
Firewalls, encryption (HTTPS), VPNs protect data.