hi,

SAP MM stands for sap material management  is one of the modules of SAP  erp domain that deals with material management and inventory management. it works mainly involves  with the Procurement Process, Master Data (Material & Vendor Master), Account Determination & Valuation of Material, Inventory Management, Invoice Verification, Material Requirement Planning, etc.

there is various shortcut of  transaction code which known as sap t code you have to master while write code. sap tutorials, tutorials point sap brain like website would be helpful to master sap technology.