Versionner is tool for creating configurations.
A Configuration determines the dependencies between packages. More precisely, the dependency between a version of a package and a particular version of a required package.
This tool is a GUI for Metacello that allows you to use a nice (but limited) tool instead of writing configurations by hand.
Metacello is a package management system that declares dependencies between those packages in configuration classes.
Monticello is our SCM system that groups code into packages.
For a tutorial video on how to use Versionner:
I hope I didn't make any mistakes.
Cheers.