I am trying to understand what congress cannot do, but its confusing.

Check Section 9 of Article I.

http://www.law.cornell.edu/constitution/constitution.articlei.html

Thanks for the link, however, It is very hard to understand. Do you know where I can find it in kids terms?

See if this site helps you understand this article.

http://www.usconstitution.net/xconst_A1Sec9.html

This site gives a short overview
http://caselaw.lp.findlaw.com/data/constitution/article01/45.html#1

Thanks the summary was a great help!

Understanding what Congress cannot do can be challenging due to the complexity of the subject. However, I can help explain some limitations imposed on Congress.

1. Constitutional Constraints: Congress is bound by the United States Constitution, which sets forth certain restrictions on its powers. For example, the Constitution outlines specific areas where Congress has the authority to legislate, known as enumerated powers, while reserving other powers to the states or individuals.

2. Bill of Rights: Congress is prevented from infringing upon certain fundamental rights protected by the Bill of Rights. These include the rights to free speech, religion, and assembly, as well as protections against unreasonable searches and seizures.

3. Judicial Review: Congress cannot pass laws that violate the Constitution as interpreted by the judiciary. The Supreme Court has the power of judicial review and can invalidate laws that it deems unconstitutional.

4. Limits on the States: While Congress has broad authority to legislate in certain areas, it cannot interfere with powers reserved to the states. This is known as the principle of federalism, which ensures a balance between federal and state powers.

5. Prohibited Actions: The Constitution explicitly prohibits Congress from taking certain actions. For instance, it cannot pass ex post facto laws (which retroactively criminalize conduct), grant titles of nobility, or suspend the writ of habeas corpus, except in cases of rebellion or invasion.

To gain a comprehensive understanding of Congressional limitations, it is recommended to study the U.S. Constitution, especially the specific articles and amendments that outline the scope of Congress's powers, as well as Supreme Court decisions that have interpreted and clarified those limitations.