Components are larger extensions that produce the major content for your site. Each component has one or more "views" that control how content is displayed.In the Joomla! administrator there are additional extensions suce as Menus, Redirection, and the extension managers.
The content component (com_content) is what you use to write articles. It is extremely flexible and has the largest number of built in views. Articles can be created an edited from the front end, making content the easiest component to use to create your site content. Help
The contact component provides a way to provide contact forms and information for your site or to create a complex directory that can be used for many different purposes. Help
The search component proviedes basic search functionality for the information contained in your core components. Many third part extensions also can be searched by the search component. Help
News Feeds (com_newsfeeds) provides a way to organize and present news feeds. News feeds are a way that you present information from another site on your site. For example, the joomla.org website has numerous feeds that you an incorporate on your site. You an use menus to present a single feed, a list of feeds in a category, or or a list of all feed categories. Help