The Legislative branch is bicameral (having two chambers or branches). It includes the Senate and the House of Representatives.
This separation is so that the Legislative branch does not get too much power.
The main job of Congress is to make laws.
The Process of Making Laws (Simplified):
Representatives/Senators write a new law (called a bill)
Senate and House debate about the bill, making changes.
After the House of Representatives and Senate on what the bill should contain, each chamber votes on it.
If the bill passes the vote in both the House and the Senate, it's sent to the President, who can either veto or do nothing
If the President does nothing, then the bill is passed into a law
If the President vetoes it and suggests other changes, then the bill goes back to Congress who can then override the veto by a two-thirds vote by both the House and Senate.
Other Powers of Congress:
Lay taxes
Collect taxes
Coin and grants money
Create post offices
Declare war
Create and fund the branches of the US military
Create courts that are lower than the Supreme Court of the United States