How Washington Actually Works For Dummies
Congress exists to prevent the executive branch in Washington DC from exercising total control over U.S. legislation. The primary job of Congress is money and the budget — a subject that, one way or another, touches the daily lives of every American citizen.
While Congress is often seen as a group that slows rather than expedites the process of democracy, its function as a body of debate and compromise is essential to the health of the American experiment.
Members of Congress determine how much, how often, and in what circumstances to tax the American people. They also decide how tax revenues are appropriated and spent across the entire federal government. (Most of your tax money is actually spent by the executive branch, although Congress and the federal courts also have their own budgets.)
Though both the Senate and House have equal authority, only the House is authorized to originate revenue and appropriations bills. (And the House is more beholden to popular opinion than the Senate because of its structure.)
Source: Dummies.com