Indexes all publications of the United States Government Printing Office. This does not mean all govenment publications. Among those excluded are NTIS Research Reports, ERIC Documents, patents, federal court cases, etc.
Indexes books, reports, maps, periodical titles (but NOT individual articles), hearings, etc. The Government Documents Department on the 5th floor of Alden Library has about 75% of the items listed. This department also has printed copies of the Monthly Catalog covering the years 1885 through 1977.
When using this database, be sure to record the SuDoc number. This is the call number you need in order to find the materials in the Government Documents Department.