External data, such as RSS feeds, weather, news, etc, are really useful things to be able to automatically add in to your signage system.

External Sources are set up on the feeds page, and deliver into various feeds, as you decide.

The different kinds of sources are defined here, in pretty much the same manner as post types. Read that documentation, and have a look at the rss post kind source, and it should make sense.

The main external Source Types:

The RSS Source Type