Every piece of content in Drupal is of a particular type. Drupal comes with two preconfigured content types, "Page" and "Story":

Page
A page doesn't show a posting date, and doesn't appear in the site's front page teaser list. Use a page for static areas of your site, such as About pages, contact details, and so on.
Story
A story appears in teaser form on the site's front page, and also shows when it was created and the author's name. Use stories to create topical posts on your site's front page.

These defaults serve as preconfigured examples and can be changed. To change these settings go to Administer > Content Management > Content Types.

To change whether the posting date and submitted by information displays, go to Administer > Site Building > Themes > Configure > Global.

Different content types have different settings (for aspects such as comments, file attachments, permissions) and can be themed differently.

Additional content types become available as you enable other modules. For example, the blog module will add a blog post content type.

You can also create your own content types to further differentiate content on your site. To add a basic, new content type (Title and Body Fields only), go to Administer > Content Management > Content Types and select the Add Content Type tab.

If you need additional custom fields in your new content type, download and enable the Content Creation Kit (CCK) module. CCK is perhaps Drupal's most widely used contributed module. For more information, see the CCK documentation.