When a host communicates on the wire, it may send, as an arbitrary example, a sequence of 48 bits at one time onto the wire. This sequence of 48 bits is referred to as a packet. A packet is a discrete number of bursts onto the wire whose contents are understood by the hosts connected on the network. Computers use this etiquette when speaking to one another. This is called a protocol.
Network protocols are the subject of a future installment.
This exchanging of packets between computers on a network is referred to as a packet-switched network. Although this term isn't commonly used outside of academic lectures, this concept of breaking up of data into pieces, packets, is the fundamental concept of network operation. A LAN is not limited to a few hosts and one network segment. A LAN typically can range in size to hundreds or even thousands of hosts on multiple networks. The breadth of a LAN can be limited in size to one building or as large as a corporate campus.