Backbone in a computer network is the innermost conduit which is designed to transport traffic at a very high speed amongst attached systems. The core idea of its existence is to make best use of a network by achieving reliability, all-encompassing performances and long-distance improved data communications. 
Internet backbones can be the best example of it. As a component of the network’s infrastructure, backbones interconnect its poles-apart elements along with offering a reliable pathway between remote LANs or sub networks just for the consistent exchange of data.
On average, backbones are consisted of the routers and switches within a network. These devices (routers etc) are connected with each other by Ethernet cable or fiber optic. Though, outsized businesses are linked nowadays to these backbones but organization’s computers can access such backbones in a roundabout way, no direct right of entry is available. Anyhow, internet service providers (ISPs) networks can be straightforwardly connected with the backbones. Moreover, you will observe somewhat a difference between backbones working at local level and operational on the internet. In case of local network, backbone is referring to a line up or gathering of lines with which LAN has access to WAN. Furthermore, backbone can cover distances professionally within building’s network well. A large transmission line carries information anyway that drawn together from other intercepted smaller lines.
As mentioned above backbone can be restricted to a single building but it can also tie up several networks within a campus environment. And fault tolerant ring arrangement by FDDI provides a sound support to a campus backbone. But according to another approach it can connect more than a few networks over WAN (wide area network) links. That means, two main topologies of backbones can be arranged practically, such as one (distributed) is possible when a connection point is provided to LANs it can be weaved throughout building premises in the form of distributed backbones but collapsed backbones be present in form of wiring hubs or switches. But third form hybrid can be achieved with the combination of both previously discussed topologies in which distributed and collapsed backbones technologies are tied up jointly.
On the other hand, backbone intended for the internet or WAN (wide area network) is a set of paths with which other local networks are connected to for long distance physical interlinks purposes. But these interconnecting points are referred as nodes. At any rate, bbackbones can fix different networks together either within a building premises or different buildings. These are very useful tools for large organizations that have many business locations or branches over a wide area so having a backbone network will be most suitable solution for them to tie up all locations together virtually as one.
In brief, backbone can be either a single box or collection of different interconnected units. But the nature of computer network as well as its backbone is based upon the requirements of a business. And only a well planned infrastructure of network backbone can be able to maintain, hold up a lot of bandwidth for all existing and potential users. So it should have an aptitude to be stretched too.