The enumerated powers are a list of specific responsibilities found in Article 1 Section 8 of the United States Constitution, which iterates the authority granted to the United States Congress. Congress may exercise only those powers that are granted to it by the Constitution, limited by the Bill of Rights and the other protections found in the Constitutional text.
The classical statement of a government of enumerated powers is that by Chief Justice Marshall in McCulloch v. Maryland:
"This government is acknowledged by all, to be one of enumerated powers. The principle, that it can exercise only the powers granted to it, would seem too apparent, to have required to be enforced by all those arguments, which its enlightened friends, while it was depending before the people, found it necessary to urge; that principle is now universally admitted."