Close to you
Start with you. Your phone, watch and earbuds talk over Bluetooth, a short-range radio, or a USB cable. Together they form a PAN, a personal area network: a few metres across, centred on one person.
Zoom out to the home. A network cable (Ethernet) joins the laptop to the router. Devices in one building, on equipment you own, form a LAN, a local area network: fast, and free to use once bought.
The phone also joins the home Wi-Fi, so it belongs to the PAN and the LAN at once. A LAN whose links are radio waves is a WLAN, a wireless LAN. Wi-Fi reaches tens of metres; Bluetooth about ten.
Campus and city
A school with several buildings joins their LANs with its own fibre-optic cables, which carry light. That is a CAN, a campus area network: up to a few kilometres, still owned and run by one organisation.
Zoom out to the city. A provider's fibre ring links homes, campuses and offices across tens of kilometres. That is a MAN, a metropolitan area network. You rent a connection to it; you do not own it.
Wide area
Cities are joined by long links, usually leased from carriers, the big telecom companies. A network spanning cities or countries is a WAN, a wide area network. Light in fibre crosses 1,000 km in about 5.0 ms.
The internet is the biggest WAN. It is not one network but millions of separately run ones, from homes and schools to carriers and data centres, joined to each other by routers: a network of networks.
Working from home, the laptop joins the office network in city B. A VPN, virtual private network, wraps each packet in an encrypted outer packet and sends it across the internet: a private tunnel built on a WAN.
Side by side
Bigger area, bigger trade-offs. A PAN spans metres, a LAN a building, a MAN a city, a WAN the world. As the area grows, links get longer and slower to cross, and more of them belong to someone else.
What is happening
;; step 1/9 · pan
;; about: pan
PAN personal area network
devices phone · watch · earbuds
links Bluetooth radio, about 10 m
or a USB cable, up to 5 m
speed Bluetooth: up to 3 Mb/s
owner you
The sizes are typical, not hard limits: names describe roughly how much ground a network covers. A Bluetooth class 2 radio reaches about 10 m; Ethernet over copper (IEEE 802.3, 1000BASE-T) is specified up to 100 m per cable. Signal times use the same rule of thumb as the "Bits on the wire" lesson: about two-thirds of the speed of light, 200 km per millisecond, so 1,000 km takes about 5.0 ms. Real paths are longer than a straight line and add waiting in routers.