What is a network?

Key takeaways A network is nothing more than devices connected together so they can share data. A small one in your home or office is a LAN (Local Area Network); one that stretches across long distances is a WAN (Wide Area Network). The internet is the biggest network of all — really a network of networks, where countless independent networks interconnect into one global system. Nobody owns the whole thing; it works because everyone agrees to connect.

Before you can reason about web requests, servers, or security, it helps to be crystal clear on the thing underneath all of it: the network. The idea is simpler than the jargon suggests, and once it clicks the rest of this path falls into place quickly.

A network has two ingredients. The first is nodes — the devices that take part. Your laptop, your phone, a server in a data centre, and the little router in your hallway are all nodes. Anything that can send or receive data counts.

The second is links — the connections between nodes. A link might be an ethernet cable, a Wi-Fi radio signal, or a strand of fibre-optic glass. The physical form doesn’t matter much at this level; what matters is that a link carries data from one node to another.

Put them together and you have the whole definition: a network is nodes plus links, sharing data. Two phones swapping a photo over Wi-Fi are a network. So is a company with thousands of machines. The scale changes; the idea doesn’t.

LAN vs. WAN

Networks are often described by how much ground they cover.

A LAN, or Local Area Network, is small and local — the devices in your home, a single office, or one school building. The nodes are close together, the links are fast, and usually one person or organisation owns and controls the whole thing. When your phone and laptop are on the same Wi-Fi and can see each other, that’s your LAN.

A WAN, or Wide Area Network, spans distance — across a city, a country, or the planet. WANs stitch many separate LANs together over long-haul links. You don’t own a WAN; you connect to one. The neat mental picture: your LAN is your own little world, and WANs are the roads that link your world to everyone else’s.

The internet is a network of networks

Here’s the part that surprises people. The internet is not one giant network owned by one company. It’s a network of networks — countless independent networks that each agree to interconnect.

Your home LAN connects to your internet service provider’s (ISP’s) network. That ISP connects to other ISPs and to large carrier networks. Businesses, universities, and cloud providers all run their own networks and plug into the same web of connections. The devices that pass data between these separate networks are routers, and the whole tangle is held together by a shared agreement to speak the same language and forward each other’s traffic.

Because it’s built this way, no one owns the internet. There’s no central switch to flip. It keeps working because interconnection is in everyone’s interest, and because the rules for connecting are open and agreed upon.

Finding each other

If a network is going to deliver data to the right place, every device needs an address — a unique label, much like a postal address, that says where data should go. On the internet these are IP addresses.

But numeric addresses are awkward for people to remember, so we also use names. When you type a friendly name like a website’s, a naming system quietly looks up the numeric address hiding behind it. That system is DNS, and we’ll come back to both ideas in detail later in this path.

Why developers care

Almost no useful program lives entirely on one machine anymore. An app fetches data from a server, a game syncs with other players, a script calls an API in the cloud — nearly every program you write ends up talking to another machine over a network.

That means understanding the network isn’t a networking-specialist topic; it’s part of understanding how your software actually connects to the world. When you know how data moves from node to node, debugging a request that won’t go through stops being guesswork. We’ll trace exactly that journey in how a web request works.

Quick check: what is "the internet", in one phrase?

Recap

  • A network is just devices connected together to share data.
  • The devices are nodes; the connections between them are links.
  • A LAN is small and local; a WAN spans long distances and links networks together.
  • The internet is a network of networks — independent networks interconnected by routers and ISPs, owned by no one.
  • Devices find each other by address, and people use names that map to those addresses.
  • Almost every program talks to another machine, so the network is core to how software connects.

Next up: packets & switching