Ivy

all you need if Ivy is properly installed is to define an XML namespace in your Ant file (xmlns:ivy="antlib:org.apache.ivy.ant"). Then all the Ivy ant tasks will be available in this namespace

http://ant.apache.org/ivy/history/2.1.0-rc1/tutorial/start.html
Without any settings, Ivy retrieves files from the maven 2 repository. That's what happened here.
The resolve task has found the commons-lang and commons-cli modules in the maven 2 repository, identified that commons-cli depends on commons-logging and so resolved it as a transitive dependency. Then Ivy has downloaded all corresponding artifacts in its cache (by default in your user home, in a .ivy2/cache directory). Finally, the retrieve task copies the resolved jars from the ivy cache to the default library directory of the project: the lib dir (you can change this easily by setting the pattern attribute on the retrieve task).

Configurations are very important concept in ivy. They allow you to group artifacts by meaning.
When you write ivy file for projects that are supposed to be reused, use configurations to allow people to get only they what they need without having to specify it by hand using artifact tag in dependency section.