Materials Management module in SAP consists of several components and sub-components. The most prominent and widely used are Master Data, Purchasing and Inventory.
All of these components have their subcomponents that are essential in specific business processes, and all of the processes are executed by using transactions.
Transaction (in SAP) means processing of certain information in order to complete business process requirement. For example, if you have purchased 10 pieces of litter buckets, you can perform particular transaction code (t-code) that will reflect those changes in SAP. Most of the business processes involve multiple SAP transactions to be accomplished and are spread over one, two or more modules.