Checks and Balances
How the three branches keep each other from getting too powerful.
The Founders designed three branches of government — Legislative (Congress), Executive (President), and Judicial (Courts) — specifically so no single branch could accumulate too much power. Each branch has tools to check the others.
Congress checks the President by: controlling all federal spending (the President cannot spend money Congress hasn't approved), confirming or rejecting presidential appointees (Cabinet members, judges, ambassadors), ratifying or rejecting treaties (Senate only, requiring a two-thirds vote), overriding presidential vetoes (requiring a two-thirds vote in both chambers), and impeaching and removing the President for "high crimes and misdemeanors."
Congress checks the Courts by: confirming or rejecting federal judge nominations, setting the number of Supreme Court justices, defining the jurisdiction of lower courts, proposing constitutional amendments to override court decisions, and controlling the courts' budget.
The President checks Congress by: vetoing legislation, issuing executive orders within existing law, and using the "bully pulpit" to rally public opinion. The Courts check Congress by: striking down laws that violate the Constitution (judicial review).
When you see Congress investigating the executive branch, holding confirmation hearings, or threatening to withhold funding — that's the system working as designed.