The Dissolve tool is used to simplify or generalize a data layer based on a common attribute value. So, for example, if you had a parcel layer that showed each parcel and each parcel was coded with its designated zoning classification and you wanted to know the total amount of area for each zoning classification within the city, the Dissolve tool can be used to create individual polygons for each zoning classification.
The Dissolve tool can be found in the Data Management Tools toolbox and the Generalization toolset. It works on points, lines, and polygons. Here is an illustration of the example that was described earlier:
As shown in the previous screenshot, the initial parcel layer contained many individual polygons that would have made determining the total area for each zoning classification difficult. Once you use the Dissolve tool, a new layer is created so that each zoning class has a single polygon. From there...