A local area network (LAN)
Connects devices within a single office or home or among buildings in an office park. The key aspect here is that a LAN is owned entirely a single organization.
The LAN is the network familiar to office workers all over the world. In its simplest conception, it can consist of a few personal computers and other periferals such as a printer.
A wide area network (WAN)
Consists of a connectivity between LANs over widely separated locations. The key aspect here is that a WAN can be either publicly or privately owned.
One advantage of a WAN is the possibility of spreading the cost of ownership among multiple organizations.
WANs come in many configurations. In its simplest conception, it can consist of a lone personal computer using a slow dial-up line to connect to an Internet service provider.