Master Data Management is a fairly new concept that has gained a lot of traction in the past couple years. MDM, as it's better known, is a holistic way of looking at data as it flows throughout an enterprise. Case in point, when we build data warehouses, we receive data from source systems and turn it into information that the business can use; painting a picture if you will for the business to see.
The data received has to come from somewhere and this is where MDM comes in. Source systems have data models, entity-relationship diagrams, cardinality models, etc. We know that each order has one customer, but one customer can have many orders (one-to-many relationship). We also know that each order can have many products. A product may or may not have a variant (a NFL Jersey has 30 variants - 1 variant for each team, and each team has many variants - a jersey for each player). So it's easy to see how this could become complicated quickly.
MDM is a methodology for watching data flow through the business, similar to a master data model. The source system contains 'orders' which them flow into the data warehouse as 'orders', and then this 'order' information is placed in reports and dashboards for measurement by the business.
Now that I've repeated myself on MDM, let's compare MDM and ETL. This actually is the reason for this post - there was a question posted on the MSDN Forums http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=1426964&SiteID=1 by a lady who was curious why ETL and MDM were not the same. In short, MDM is enterprise wide while ETL is specifically related to the data warehouse. Here is my answer:
"MDM is the overall view of managing data within an enterprise, like an umbrella over all the sources of data within a company. ETL is the process uses to support the MDM objectives for business intelligence purposes. With MDM technologies, ETL will become much simpler. MDM is a fairly young in the broader world of business intelligence and will continue to grow as time progresses."
Hopefully now you have a better understanding of the similarities and differences between ETL and MDM.