You can use the UnifiedSearchServices class to configure and start a search operation from your application. In the simplest case, you can search all data sources when you submit a keyword to the Unified Search Service. However, you can limit your search to particular searchable data sources, and search fields within those sources.
When your search is complete, the Unified Search Service returns a SearchResponse object that contains searchable entities that matched your search criteria. The Service returns the data organized by searchable data source and search field. The structure of the result allows you to look at the metadata that is related to the result. In this way, you can make more detailed decisions about the relevance of search results to your users.