The banner module is used to display the banners that are managed by the banners component in the site administrator. 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 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