layer 2 - Definition from the Hotspot Shield Glossary
Layer 2 of the OSI Reference Model (Open Systems Interconnection) is the Data-Link layer. The Data-Link layer is responsible for the movement of data packets or datagrams along the physical route of as network.
This layer is split into two sublayers - MAC sublayer and LLC sublayer - The MAC is the Media Access Control that is used to identify the destination address, and the LLC determines the logical route that the data should take. Layer 2 ensures that a connection is established, ensures that the data has been received in the form of acknowledgments, splits output data into individual frames and analyzes bit patterns to ensure that incoming data is received.