What is SAP R3 Architecture ?

What is SAP R3 Architecture
SAP R/3 is one of the main product of SAP,where R stands for RealTime and the number 3 relates to three tier application architecture(Data base,Application Server and Client).
Most of the business in todays world runs on SAP R/3 system.About 80% of the companies implemented this software.
SAP R/3 Architecture
SAP based architecture of R/3 on a three-tier client/server model.
Presentation Server
Application Server
Database Server