Hubs were the common network infrastructure devices used for Local Area Network (LAN) connectivity but network switches are rapidly replacing hubs. These days it is very difficult to spot a Network Hub functioning in a live Local Area Network (LAN). Hubs function as the central connection point for Local Area Network (LAN). Hubs are designed to work with Twisted pair cabling and normally use RJ45 jack to connect the devices. Network devices (Servers, Workstations, Printers, Scanners etc) are attached to the hub by individual network cables. Hubs usually come in different shapes and different numbers of ports.
When a hub receives a packet of data (an Ethernet frame) at one of its ports from a network device, it transmits (repeats) the packet to all of its ports to all of the other network devices. If two network devices on the same network try to send packets at the same time a collision is said to occur.
Hubs are considered to operate at Physical Layer (Layer 1) of OSI model. An 8 port hub is shown below.