What is Meant By SAP R3

We know that SAP R/3 is software, it particular it is client-server software. This means that the groups/layers 
that make up a R/3 System are designed to run simultaneously across several separate computer systems. 

When you install Microsoft Excel on your PC, each component of Excel (printing components, graphing components, word processing components, and etc.) is stored, managed, and processed via the hardware of your PC.   When a company installs SAP’s software each component (or "layer” in R/3’s case) is stored, managed, and processed via the hardware of separate and specialized computer systems. Each of the various layers is capable of calling upon the specialty of any of the other installed layers in order to complete a given task. 

Those components/layers that are requesting services are called “clients”, those components/layers that are providing services are called “servers”.