As each piece of data from your original dataset is mapped into a category, it's automatically converted into one or more representations.
The representations available for each category are defined by the Global Schema. Every category has at least one representation, and many have more than one.
At its simplest, a representation is a standardised way of formatting values. For example, two datasets might use different date formats in their original data, but the standardised representation of a date will be the same for both of them.
But some representations do more than that - reflecting interpretation or analysis of an item of data. For example, the category called Occupation has representations called Industry and Seniority. In this way, the complex and multi-faceted information contained in a job description is broken down into specific details, which can then be accessed in queries and reports.