Network Interface Card (NIC)
Any computer that is to be connected to a network, needs to have a network interface card (NIC).

Most modern computers have these devices built into the motherboard, but in some computers you have to add an extra expansion card (small circuitboard)

Some computers, such as laptops, have two NICs: one for wired connections, and one for wireless connections (which uses radio signals instead of wires)

In a laptop, the wireless radio antenna is usually built in to the side of the screen, so you don't need to have a long bit of plastic sticking out the side of your computer!
Network Cable
To connect together different devices to make up a network, you need cables.

Cables are still used in most networks, rather than using only wireless, because they can carry much more data per second, and are more secure (less open to hacking).

The most common type of network cable cable in use today looks like the one shown above, with plastic plugs on the ends that snap into sockets on the network devices.

Inside the cable are several copper wires (some used for sending data in one direction, and some for the other direction).
Hub
A hub is a device that connects a number of computers together to make a LAN.

The typical use of a hub is at the centre of a star network (or as part of a hybrid network) - the hub has cables plugged into it from each computer.

A hub is a ‘dumb’ device: if it receives a message, it sends it to every computer on the network. This means that hub-based networks are not very secure - everyone can listen in to communications.

Hubs are pretty much obsolete now (you can't buy them any more), having been superseded by cheap switches.
Switch
A switch, like a hub, is a device that connects a number of computers together to make a LAN.

The typical use of a switch is at the centre of a star