At the CentOS Dojo Brussels 2015 Honza Horak presented on Software Collections. Starting from what they are, how they work and how they are implemented. During this 42 min session he also ran through how people can create their own collections and how they can extend existing ones.
Software Collections are a way to deliver parallel installable rpm tree’s that might contain extension to existing software already on the machine, or might deliver a new version of a component ( eg. hosting multiple versions of python or ruby on the same machine at the same time, still manageable via rpm tools )
This Video is now online at https://www.youtube.com/video/8TmK2g9amj4
You can get the slides from this session at the event page on http://wiki.centos.org/Events/Dojo/Brussels2015