SAP PP (Production Planning) is one the largest functional module in SAP. This module mainly deals with production process like capacity planning, Master production scheduling, Material requirement planning shop floor etc. The PP module of SAP takes care of Master data needed like Bill Of Materials ( BOMs), Routing and Work Centers and stores it in one separate component. 

SAP PP is mainly divided into planning and execution. Planning contains materials planning and capacity planning. Materials planning can be done for different lengths: long term planning, material requirements planning etc. Execution contains creation of production order, scheduling, work flow (such as release printing), confirmations, goods movements, technical completion.

Most of the above mentioned sub processes need master data to be maintained. And when you carry out, they generate transactional data like planned orders, production orders, accounting documents etc. Also, there are sub modules for different types of industries like discrete production, process production (like chemicals), repetitive production, kanban, all these normally follow the above mentioned sub processes.