The concept of a semantic layer being compared to an operating system is discussed, emphasizing that the layer should not only translate but also determine where to execute. The speaker highlights the misconception that a semantic layer is just a magical translation tool, when it should be seen as an operating system that handles execution. The distinction between semantic layers and master data management (MDM) is explained, with the assertion that MDM is essentially a type of semantic layer, differing only in the application of business rules at object and field levels compared to schema level.