A network topology is the arrangement of all the elements in a network.

Bus topology -

Devices are connected to a central backbone cable. If the central cable breaks all the devices lose their connection.

Ring topology -

Devices are connected by a ring cable. Like in a bus network, if the central cable breaks all the devices lose their connection. This can be prevented by adding a second ring, but that requires a lot of additional cabling.

Star topology -

Devices connect into the central switch. It is the most popular wired type of network. If a cable breaks only that computer is affected, but if the switch breaks all the computers on the network are going to lose their connection.

In the past star networks used hubs rather than switches. A hub broadcasts the traffic to all of the devices on the network, causing lower security and lower bandwidth because of the increased traffic. A switch solves those problems by making sure that traffic is only directed to the computer it was intended for.

Full mesh topology -

Every device is connected to every other device. If there is a break in any of the connections, traffic can still be sent via another route. A lot of cabling and switch hardware is needed which can be expensive.

Partial mesh topology -

Multiple connections exist between devices, but not every device is connected to every single other device. It requires less hardware than a full mesh network