Sometimes multi-sites do not need to share content, but would benefit from sharing content types, permissions, views, contexts, formats, and other structural data. Typically, this data is stored in the database, and since Drupal multi-sites typically do not share the same database tables, they cannot automatically share this data.
However, the Features module (http://drupal.org/project/features) provides this capability. Features is a tool that transforms certain Drupal structures into versioned modules.
Note
Features is by no means specific to multi-site configurations. Most commonly, it is used to share features between completely unrelated sites.
Let's imagine a practical scenario. Imagine that we have created a blog. On one of the sites in our multi-site we have defined the content type, the permissions, and the views necessary for this blog. But now we want to use this exact blog structure on all of the sites on the multi-site. This is what Features allows us to do....