I am having a doubt in the below paragraph.
When a user executes a search from the search dialog or widget, the system starts your searchable activity and sends it a ACTION_SEARCH intent. This intent carries the search query in the QUERY string extra.
What is string extra in the above paragraphs last line?
You can read about all the details of Creating a Search Interface but I’ll give you a brief overview of how this works:
First off, a searchable activity is the Activity in your application that performs searches based on a query string and presents the search results.
When the user executes a search in the search dialog or widget, the system starts your searchable activity and delivers it the search query in an Intent with the ACTION_SEARCH action.
Your searchable activity retrieves the query from the intent’s QUERY extra, then searches your data and presents the results.