Each of the layers in a map has a set of properties that can be viewed, allowing you to learn the functionality available for that layer.

To view a layer's properties, right-click the layer in the ArcReader table of contents.

On the General tab you can see whether the layer will be displayed at all scales or only within a specific range of scales. You can also see whether MapTips have been enabled for the layer and which field has been chosen to be displayed in the MapTips. MapTips are on screen descriptions of map features that appear when you point to a feature.