Then there are many class that represents Umbraco documents:
1) umbraco.cms.businesslogic.Content
2) umbraco.cms.businesslogic.web.Document
3) umbraco.MacroEngin
Content allows you to retrieve/edit any content (page/media/..) from DB (including non-published content), Document allows you to retrieve/edit only page content from DB (including non-published content), Node is used for fast read-only access to (published only) page content from the XML cache and Dynamic Node is comparable to Node but implemented in later versions of Umbraco for macros using Razor