A Hub is basically a centralized device which has multiple ports associated with it. Each of these ports are connected to different computing devices via wires or cables, hence Hub is helps multiple devices to share data with each other,& hence Hub sometimes called as a Multiport Repeater. The problem of using Hub is that it is not an intelligent networking device i.e. it doesn’t has the capability to filter data, so when any signal or message comes from one of the device connected to it it simply broadcasts the message to each & every device connected with it , instead of sending that message to the intended location. There is only a single Collision Domain in case of Hub, every communication taking place has to go through Hub i.e. if multiple messages from different devices reaches Hub at the same time then the messages will collide with each other & there will be loss of data.Hub works in Physical layer of the OSI model as it is a physical device.
There are mainly 2 types of Hubs:
1) Active Hub :
This type of Hub rely on power supply for it’s working.It has the capability to filter & amplify data signals if needed & thus it can also be used as a repeater.
2) Passive Hub :
This type of Hub doesn’t need any kind of power supply for it’s working,& it transmits data to all other devices connected with it as it is , as it doesn’t amplify the signal.