How do mobile applications (such as Facebook) access web pages without using a browser?


How does mobile applications( like fb, linkedin,…) access a web page with out a web browser? Do these apps have an inbuilt web browser or do all apps share a common web browser in the phone? Do these apps also use javascript to display web pages like browser? My question is who does the job of web browser in android app? Who displays html pages and works on javascript if no browser is present?

Some apps have webviews embedded in them that display a web page straight from the source. But some (like Facebook) fetch data and dynamically display data on the screen.