What are the 3 categories in which the constitution divides power in the United States

Assuming that you mean the 3 different branches of the government in which power is seperated equally, those branches would be ...

Executive Branch, Judicial Branch, Legislative Branch.

These branches of government are seperated and have their own duties on governing the land. Checks and Balances is what it is known by

Executive - The President of the United States & Commander in Chief

Judicial - The Supreme Court

Legislative - Congress (House of Representative and Senate)