OneJar "Enter Java Package Name"

Question

I'm trying to build my project, with contains multiple other JARS and natives, into one fat jar. I was pointed into using the onejar project, which can be found here: http://one-jar.sourceforge.net

When running one jar with the command line, I am prompted with

Enter project path (project name is last segment): c:/tmp/test-one-jar
Enter java package name: com.example.onejar

I put in my prioject directory for the first question, but I am confused what the second prompt is asking for. What does it mean by java package name? Thanks for the help.