Meta Data: Data that describes the structure of data or MetaObjects is called Metadata. In other words data about data is known as Meta Data.
Master Data: Master data is data that remains unchanged over a long period of time. It contains information that is always needed in the same way. Characteristics can bear master data in BW. With master data you are dealing with attributes, texts or hierarchies.
Transaction data: Data relating to the day-to-day transactions is the Transaction data.