What is the differences between star topology and bus topology?

Answer 1

A star topology has a central hub with other devices each connected to the hub but not to each other - for one device to communicate to another, they have to use the hub.

With a bus topology all the devices are connected to the same bus - there is no hub. Each topology has advantages and disadvantages; the speed of a star network is limited by the hub; a telephone exchange is an example of a star network and there is a built-in limit to the number of devices that can be connected and there's no way to increase it other than to replace the hub with a bigger one. However, the devices (telephones in our example) can be dumb - all the intelligence is in the hub; it manages the calls and importantly, for commercial exchanges, calculates the bills. For bus networks, devices have to be smarter but can do much more as they can grab the whole bus.