220-301 220-302 N10-003 SY0-101 640-801 640-821 640-811 Subnetting 70-210 70-216 70-218 70-270A LAN (Local area network) is defined as a group of computers that are restricted to a single geographic location. Typically this would be an office or even office building. Depending on the vintage it could be a Bus topology, using Thicknet or Thinnet. As a field tech you will see that this is still not uncommon. On the other side of the coin it could be Gigabit Ethernet network! LANs are typically faster that WANs.
A MAN (Metropolitan area network) widens the range of a LAN considerably. It could be a city with many connected LANs, a College campus or a hospital facility.
A WAN (Wide area network) covers more than one geographic location, and could be world wide, although it does not have to be. The Internet is a WAN.