Learn Organic groups
Organic groups is a module usually used for creating "groups" – containers for content (and other entities), which can have members. The memberships can then be used for controlling access to group content in different ways.
(Photo cred to krayker at rgbstock.com.)
Organic groups is undergoing some significant changes. I am halting this screencast, to follow up on those changes before recording more episodes about Rules and Views integration. Sorry.