This is an example environment directory. The environment's modules can be
placed in a "modules" subdirectory. The environments initial manifests are
placed in a "manifests" subdirectory. By default the environment also has any
modules that are installed globally (normally in /etc/puppetlabs/code/modules) for the
puppet master.

For more information see
http://docs.puppetlabs.com/puppet/latest/reference/environments.html