The home search page for the National Archives is located here: https://www.archives.gov/research/catalog

The rights and permission statement may be found here: https://www.archives.gov/global-pages/privacy.html

The National Archives houses images, documents, film, audio recordings, and other material collected by a multitude of government agencies.  As the work of the US government, these items are copyright free and are free for the public to use, although some material that was gifted to NARA has limitations and restrictions.  It offers various resources for researchers, including HistoryHub where researchers can collaborate and raise questions about specific archival collections and records (https://historyhub.history.gov/welcome).  The site is a good source for information related to US history, government programs, genealogy, and military history.