Congress is the legislative branch of the federal government. Article I gives Congress the power to make federal law, raise revenue, borrow money, regulate commerce, create lower federal courts, declare war, support the military, govern naturalization and bankruptcy, protect intellectual property, and make laws necessary and proper for carrying out federal powers.

Congress controls federal taxing and spending. Agencies generally cannot spend money unless Congress has authorized and appropriated it. Budget fights, shutdowns, debt-limit disputes, emergency funding, and program design all flow from this spending power.

Congress can investigate public problems, examine agency action, request records, hold hearings, issue subpoenas through proper procedures, and use oversight to inform legislation or expose failures. Oversight is strongest when tied to a valid legislative purpose.

Congress can confirm many presidential nominees through the Senate, impeach and try federal officials, regulate the jurisdiction of lower federal courts, change statutes after court decisions, require reports, set budgets, and create or reorganize agencies.

Congress can tax, spend, borrow, regulate interstate commerce, create federal courts below the Supreme Court, declare war, raise and support armed forces, admit states, investigate public programs, and write laws needed to carry out its enumerated powers. Those powers are strongest when Congress acts through a clear statute, appropriates money, or sets conditions on federal programs. They are weaker when Congress tries to control subjects reserved to states or individual rights protected by the Constitution.

For the legal foundation, start with Article I of the Constitution. For how Congress is using power now, look at bill text, committee reports, appropriations language, roll-call votes, and oversight hearings.