Components are containers that help display pieces of content on a page in a particular format. Components aren't pages, but they are used in conjunction with pages to display certain types of content and provide additional functionality a page alone may not provide on its own.
Components have an xID, but unlike pages, do not have a URL on the live website. The content of most components can only be viewed on the live website when linked to or embedded within a compatible page.
You can create new or edit existing components as you would a new page. For the basic process, see the Editing in Workflow section of this guide.