What branch of the government passes bills?

In the United States system of government the branch that passes bills is the legislature, the US Congress. Any member of Congress can introduce a bill but only members of the House of Representatives can introduce bills relating to taxes and spending. Wherever the bill is introduced it must pass through both houses before it can become law. The process in both the Senate and the House is almost the same, involving a lengthy examination of proposed legislation by committees.
If a bill is then passed by one house, it's sent to the other. A joint committee of the House and Senate attempts to work out any differences. If both houses agree to the bill then it is signed by the Speaker of the House and the Speaker of the Senate, who is also the Vice President. Once signed, the bill is then sent to the president for his signature.