The drawing you used in
Lesson 2: Clean Up Your Drawings contains object data. Object data consists of attributes of the real-world objects that the drawing objects represent. The object data is stored in the map itself and is associated with individual drawing objects.
When you export drawing objects, you can use object data to create feature classes in an SDF file. The resulting feature classes have properties that correspond to the object data attributes.
In this exercise, the street centerlines in the drawing have three object data attributes: Lanes, Speed_Limit, and Surface.