Hub (layer 1 DEVICE):

• Hubs, also known as repeaters, are network devices that can operate on layer-1 (I.e. the physical layer) to connect network devices for communication.
• A common connection point for devices in a network (Physical Layer-Layer1). When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.

Switch (layer 2 Device)::

• Switches are network devices that operate on layer-2 of OSI model of communication.
• Switches are also known as intelligent hubs.

 In networks, a device that filters and forwards packets between LAN segments. Switches operate at the data link layer (layer 2) and sometimes the network layer(layer 3) of the OSI Reference Model .

Router (layer 3 Device): 

• Routers are the network devices that operate at Layer-3 of OSI model of communication.
• As layer-3 protocols have access to logical ADDRESS (IP addresses) so routers have the capability to forward data across networks.
• Sometimes routers are also known as layer-3 switches.

A device that forwards data packets ALONG networks. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP [Network Layer (Layer3)]

Hub (layer 1 Device):

Switch (layer 2 Device)::

 In networks, a device that filters and forwards packets between LAN segments. Switches operate at the data link layer (layer 2) and sometimes the network layer(layer 3) of the OSI Reference Model .

Router (layer 3 Device): 

A device that forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP [Network Layer (Layer3)]