In simple words the term topologies means how we layout our computers in a network there are basically five types of topologies are there these are as follows:--
1.STAR TOPOLOGIES
2.MESH TOPOLOGIES
3.BUS TOPOLOGIES
4.RING TOPOLOGIES
5.TREE TOPOLOGIES( Let me explain you all this topologies one by one
I) STAR TOPOLOGIES
In this type all device are connected with each other through single hub by a cabel.all data are transferred from one computers to other the main disadvantage:if hub damaged all network will get lost
II) MESH TOPOLOGIES
In this each and every computer is connected to each other
so whole network form a mesh.
DISADVANTAGE: is that it takes lot of wires,and if one computer damaged whole of the network shutdown.
III)BUS TOPOLOGIES
in this type all divece are connected to a single cable in a parllel form.data is transferred from that cable to each and every device
ADVANTAGE:it uses less cable than other form for connecting devices.
DISADVANTAGE: If any fault occur in the main cable through which all device's are connected ,then all the network get disturbed.
IV)RING TOPOLOGIESALL device are connected in the form of ring.and data is transferred from one computer to other in a form of ring.
ADVANTAGE: Data Transferred from one computer to another computer in a sequential way.
DISADVANTAGE:If any fault occur in a cable during flow of data whole of the network get damaged.

V)TREE TOPOLOGIES
It is most useful one in this one hub is connected to other hub &each hub is connected with two or more device it form a branhes of tree like structure.
ADVANTAGE:if any hub is damaged it'll not affect whole of the network it is a most preffered one topologies now day's
DISADVANTAGE:It's much more costly than any other form of topologies.