The correct answer is implied powers.
Implied powers are the powers of the U.S. government which have not been explicitly granted by the Constitution. There are only implied when there is a necessity to carry out the expressed powers.
The so called 'Elastic Clause" that appears in Article I section 8 of the Constitution grants Congress the power to pass unspecified laws 'necessary and proper' for the exercise of its expressed powers.
The implied powers are not stated as such and their definition is unclear. They are difficult to interpret or understand as the phrase 'necessary and proper' can have a very broad interpretation. It can be very subjective ( what's proper for one can not be proper for another ) and so it has been extremely controversial and subject to ferocious political disagreements.