NetBIOS (Network Basic Input/Output System) is a programming interface that allows applications on different computers to communicate within a local area network (LAN). It was created by IBM for its early PC Network, was adopted by Microsoft, and has since become a de facto industry standard. In short, NetBIOS provides communication services on local networks.
NetBIOS provides two communication modes: session or datagram. Session mode lets two computers establish a connection for a “conversation,” allows larger messages to be handled, and provides error detection and recovery. Datagram mode is “connectionless” (each message is sent independently), messages must be smaller, and the application is responsible for error detection and recovery. Datagram mode also supports the broadcast of a message to every computer on the LAN.