Legislative procedures are an essential part of and purpose of existence of the United States Congress. Bill is a law in the making. It must be signed by the President after both Houses (Senate and House of Representatives) agree. Any member of the Congress can introduce a bill at any time while the House is in session.
When the bill passes the both Houses it is sent to the President for approval and signing. President then signs the bill and makes it into a Law. If the President has objections to the bill, he or she may veto the bill and return it to Congress with all the objections he or she may have. The Congress can override the veto if there is a two-third of majority. In another example, President may choose to ignore signing the bill, and if that happens, the bill automatically becomes the law in 10 days.