From the National Archives website:
Each year, our staff serves our visitors billions of letters, photographs, video and audio recordings, drawings, maps, treaties, posters, and other items that we have preserved. The materials are not for loan to the public, as a library loans material; they are protected, but are available for you to use in-person at our facilities and affiliated archives.
What is available from the National Archives?
You can visit National Archives locations nationwide to:
Who Uses the National Archives and Why?
Most people who come to the National Archives to conduct research are genealogists or family historians. They are trying to find information about their ancestors in order to fill in their family tree or write a family history. They use census records to learn people's names, ages, and who lived where, when. They check passenger arrival lists from boats that originated in Europe to prove when an immigrant landed in the United States. Genealogists also often look at military service records, as well as land, naturalization, and passport records, and more.
In addition to conducting this research at the National Archives Building in Washington, DC, the Regional Archives also have most of the main genealogical-related records on microfilm as well.
The National Archives website offers little genealogical content, but it has information on how to effectively use the physical holdings.
Notes and references