Define network topology and its type?

opology refers to the layout pattern in which various computers are connected to one another to form a network. The computers on a network are also referred to as nodes.
There are four main types of topologies. They are:

• Bus Topology: In bus topology, all the computers are connected to a single cable called the bus . The transmission of data from any computer travels through the length of the bus in both the directions and can be received by all other computers on the network. 
• Ring Topology: In ring topology, each computer is connected to two other computers so as to form a closed ring-like structure. In this topology, data is transmitted in one direction only. The disadvantage of the ring network is that the breakdown of any one computer on a ring can disable the entire system or network.
• Star Topology: In star topology, all the computers are connected to a central computer or a central node . The data to be exchanged between any two computers passes through the central node. The central node controls all the activities of the nodes.  
• Mesh Topology: In mesh topology, every computer is connected to every other computer on the network. Full mesh topology  is very expensive to implement. Normally, partial mesh topology is implemented in which a computer is connected to a few other computers in the network  .