When you add a topology to ArcMap, you have the option to add all of the feature classes that participate in the topology to the map as well.

Once you add this topology and its feature classes to the map you can see line and point errors. The red lines represent a new type of error feature—line errors. These show violations of the Must Be Covered By Boundary Of rule. There are two types of point errors now, violations of the Must Not Have Dangles rule, which you’re already familiar with, and violations of the Must Be Properly Inside rule.

Since there is now more than one type of point error, you will change the symbology of the Topology layer to make it clearer which errors are which. In this example, the Must Be Properly Inside errors are given a red triangle symbol to distinguish them from the other point errors.