You have just created a new topology in the previous recipe. This will allow you to find errors in the parcel feature class which violate the polygons must not overlap rule you included in the topology. To find any errors you must first validate the topology.
When you validate a topology, several things occur. First, all features participating within the topology are snapped together if they are within the cluster tolerance. This is done automatically for all features when you validate. Second, the participating feature classes are checked against the rules you have included in the topology. Any areas that include features that violate the rules are identified in the topology so you can easily locate the errors and fix them.
In this recipe, you will validate your topology to identify any errors in the Parcels feature class. To do this, you will create a new map and add the topology, along with the Parcels layer, to it.