House and Senate Documents encompass a variety of materials including:

• Reports by executive departments and agencies of government
• Reports of special investigations ordered by Congress
• Presidential messages
• Annual reports of non-governmental organizations
• Some committee prints

Documents are assigned numbers for each Congress and chamber.
Examples: H. Doc. 108-7 or S. Doc. 105-22

Senate Executive Documents contain the text of treaties submitted to the Senate for ratification. Beginning in 1981 these became known as Senate Treaty Documents.

Senate Treaty Documents contain the text of treaties submitted to the Senate for ratification from 1981 forward.

(Source: GPO Access)