Each content type has default content that appears on the new content form. The items that appear on the new content form are referred to as Fields. For example, the News/Blog content type has default fields: Title, Body, Tag, Publish Date.
Each content type has a default page layout, and each field has a default location in the layout.
After you have created a page, you can customize it to suit your needs. You can change the layout of the page, you can move the content around so it is in a different order or a different region, or you can add additional content.