Profile sonatype can be activated only manually from command line, e.g.:
$ mvn clean deploy -Psonatype
The profile will try to "deploy" your artifacts to oss.sonatype.org Maven repository, using nexus-staging-maven-plugin, "close" remote repository and "release" it.
Deployment is bound to the deploy Maven phase. The profile also skips the default deployment of maven-deploy-plugin.
The profile also automates creation of -sources.jar and -javadoc.jar artifacts, required by Sonatype.