In general, to broadcast is to cast or throw forth something in all directions at the same time. A radio or television broadcast is a program that is transmitted over airwaves for public reception by anyone with a receiver tuned to the right signal channel.
Broadcast networks refer to networks such as LANs connected by a technology such as Ethernet. Broadcast networks, by nature, are multiaccess where all routers in a broadcast network can receive a single transmitted packet.
In computer networking, broadcasting refers to transmitting a packet that will be received by every device on the network. In practice, the scope of the broadcast is limited to a broadcast domain. Broadcasting a message is in contrast to unicast addressing in which a host sends datagrams to another single host identified by a unique address.
Broadcasting is the most general communication method, and is also the most intensive in the sense that many messages may be required and many network devices are involved.