Basically, VersionCode is Google's way of keeping track of new releases, however minor or major the changes and VersionName is for you to keep track using whatever method you choose. Thus, VersionCode 1 might be VersionName 1.0 for you, VersionCode 2 might be VersionName 1.1 for you, indicating a minor fix, and VersionCode 3 might be VersionName 2.0 for you, indicating a major updated release.