Although they are not specifically mentioned in the U.S. Constitution nor defined by federal statute, Executive Orders are implied in Article II and have been considered one of the President’s powers since George Washington’s administration. Executive Orders are exactly what they sound like—orders produced by the President, as head of the executive branch, that are "generally directed to, and govern actions by, Government officials and agencies." External These Executive Orders can have the force of law, even if they do not follow the same procedure as bills passed by Congress.
It is the rather idiosyncratic nature of this process which can cause so many problems for researchers seeking information about Executive Orders. Luckily, there are several resources, both at the Library of Congress and online, that can help provide access to these researchers.