One of the cornerstone technologies present in SharePoint 2013, search is pervasive. The capability to search and render content can appear in navigation, filtering, search queries, and many other locations. Search is also capable of reaching across boundaries, surfacing content present in other line of business systems.
Result sources have two core functions:
They are used to scope search results to a certain type of content or subset of search results.
They are also used to federate queries with the local SharePoint ...