Server also applies to individuals bringing food, drinks and other consumables to you, of whom are typically tipped a percentage of the check's total
Just felt like being silly.
The replies above by ECN members are / should be just what you are looking for.
BTW a LAN (Local Area Network) doesn't absolutely require any dedicated Servers in order to function and operate as a LAN.
An example is a simple Peer-To-Peer Network. It does not specify any machine as Workstation or Server - only users/clients (ohhh, you netgeeks will kill me for using those terms!!!).
On Peer-To-Peer Networks, any machine can be used as a Server, or all machines may be Servers- all depends on what the criteria involved is and how readilly folders (directories) are shared.
More in-depth and "powerful" (so to speak) LANs utilize several servers and different types of servers (as described in Bjarney's post).
File/Servers on Large LANs / WANs may incorporate 1 to 255 stand-alone machines - each having fixed disk drives in a "RAID" configuration (Redundant Array of Inexpensive Diskfrives).
Print/Servers may be simple "Caches" which are diskless DRAM memory banks with a NIC, all in a small case (they look similar to Switches/Hubs) and are addressable via TCP/IP; others may be stand-alone PC type machines. These function to "Spool" print jobs from network workstations to one or several printers.
Communication Servers (Comm Servers) can be simple units like ADSL Bridge Routers, more sofisticated units like Cisco Routers and such, or may be a stand-alone PC type machine. The basic function here is to share Communication lines across a network. Simple example is sharing a single telephone line with two or more machines (work stations), for tasks like faxing or WAN access.
Internet Servers are like a combination of File and Comm servers. They may be Local (proxy Servers) or contained within an ISP and / or a Telco's CO (Central Office).