A more thorough explanation:

An act of Congress is a law that is created by the legislative power granted to Congress by the U.S. Constitution. In order for a bill or resolution to become an act of Congress, it must be passed by a majority of the members in both the House of Representatives and the Senate.

For example, the Affordable Care Act, also known as Obamacare, is an act of Congress that was passed in 2010. It required all Americans to have health insurance and provided subsidies for those who couldn't afford it.

When a bill or resolution is introduced in either chamber, it is assigned to a committee. If it is passed by the committee, it is reported to the full chamber. If it passes in the full chamber, it is reported to the other chamber, which then assigns it to a committee in that chamber. If it passes by majority votes of the committee and full body in that chamber, it is reported back to the originating chamber. If its terms have changed in the second chamber, it is submitted to a conference committee, consisting of members from both chambers, to work out a compromise.

Once the bill or resolution is passed by both chambers, it is signed by the Speaker of the House and the President of the Senate, and is presented to the President of the United States for signature. If the President signs it or fails to return it to Congress within ten days, the bill or resolution becomes law. But if the President vetoes the bill or resolution, it must be passed by a two-thirds majority of the House of Representatives and the Senate to become law.