Servers are high-end computers that hold data and application programs shared by all network users. Clients are the users' personal computers which provide a network access point and can perform a portion of processing depending on the system architecture. LAN system architecture can be characterized as two or three tier. System architecture refers to the structure used to organize computing responsibilities. With two-tier system architecture, the server integrates databases with a component part of the application logic while clients integrate user interface programs with the reminding portion of application logic.
Application logic refers to programs used to process and analyze data.
With three-tier system architecture, the user interface, application logic, and databases all stand alone and often reside on separate machines. To the user operating from a client machine, the networked system is perceived to be seamless. The network operating system functions as the controlling software in a LAN and resides on the server. A component part of the software resides in each client and allows the application to read and write data from the server as if it were on the local machine. The conduit through which messages and information are carried when traveling between machines and along the network backbone.