GroupId is the first coordinate of an artifact that indicates the unique identifier of the organization or group that created the project.
It's the Maven jargon for the package name.
org.apache.maven.plugins is the designated groupId for all Maven plug-ins.
Yo can define the default plugin groupId by adding the following to the settings.xml
<pluginGroups>
<pluginGroup>groupId</pluginGroup>
</pluginGroups>