The Data window contains a few fields that are not part of your data source, two of which are Measure Names and Measure Values. The Measure Values field always appears at the bottom of the Measures area of the Data window and contains all the measures of your data source collected into one field. The Measure Names field always appears at the bottom of the Dimensions area of the Data window and contains all the names of the measures collected into a single dimension.
Tableau automatically creates these fields so that you can build certain types of data views that involved multiple measures. In particular, use these fields if you want to display multiple measures in the same pane simultaneously. As shown below, creating a view with Measure Names and Measure Values is one way to display all the data in your data source.