SAP stands for Systems, Applications & Products in Data Processing and is also the name of the corporation that constructed the Enterprise Resource Planning (ERP) system of the same name. Large and medium sized corporations use ERP systems to make sure their business is effective and efficient.
The purpose of an ERP systems is to map the business processes in finance, production planning, sales and distribution, material management and others onto a group of closely related programs which, because they are well integrated, perform the required operations faster, with less errors and in greater volume then if the programs were independent.
SAP is divided into modules, out of necessity more then anything else, because SAP covers almost all standard business processes. Each module is distinct and covers only a single area such as Finance(FI), Material Management(MM) or Sales and Distribution(SD).
Businesses have very similar processes which are already implemented in SAP modules, but they need to be fine tuned to the specific needs of a business. The processes are fine tuned using the SAP Implementation Guide (IMG) or if the process is very specific, it can be accommodated in SAP using a programming language called ABAP to develop the necessary functionalities.
ABAP stands for Advanced Business Application Programming, a programming language similar to COBOL in which all SAP functionalities are implemented. ABAP is used for creating, modifying and extending all programs in SAP. Learning ABAP is hard due to the lack of pedagogically sound and also free tutorials.
SAP comes with a large package of programming tools such as an Integrated Development Environment (IDE), graphical page editor called SmartForms, tools that allow SAP to connect and communicate with other SAP and non SAP system called ALE as well as testing tools like eCATT.