What does our legislative branch of government do?

The legislative branch of government in the United States is made up of the House of Representatives and Senate, which together make up the U.S. Congress. The Congress passes legislation in a process that involves the introduction of a bill in either house and the referral of the bill to the subcommittee or committee that handles that area (for example, there are committees related to the budget, agriculture, education, and other areas). Then, the bill is amended and, if the committee votes for it, the bill is sent to the floor of the House or Senate for debate. If both houses of the Congress pass the bill, it is sent to the President, who can either sign it or veto it (if the President vetoes it, the bill can still be passed with a two-thirds majority of the members of Congress).
In addition to creating bills and passing laws, the Congress has the right to declare war. The House has specific powers, such as originating revenue bills and impeaching the President and other federal officials. The Senate has the right to confirm or reject some Presidential appointees, such as Supreme Court justices, and the Senate also tries federal officials, including the President, who have been impeached by the House. The Senate must also approve treaties related to foreign trade. The Congress also has powers of oversight over governmental operations. For example, there is a House Committee on Oversight and Government Affairs to perform checks on governmental operations. 
https://www.whitehouse.gov/about-the-white-house/the-legislative-branch/