It is the Layer two, the second lowest layer in the OSI seven-layer model.It controls the transfer of information between nodes over the Physical layer.it splits data into frames for sending on the physical layer.

• It uniquely identifies each device in the Network.
• It translates data from Network Layer into bits for the Physical
  layer to transmit.
• It formats the messages into Data Frames
• Adds a customized header containing Source and Destination
  hardware address

Devices that works at this layer are
-LAN Card
-Switches
-Bridges etc.