An idea is created and shared. It could be an idea from a senator, representative, or a civilian.
I agree! *signs*
During this process, the bill goes through committees to decide on the actual wording of it.
When enough people agree on it it becomes a bill and is sent to the House of Representatives to be voted on. Afterwards it goes to the Senate to be voted on again, or it could go the other way around. Between each stop, it goes through more committees
If the House and Senate agree to the bill, the bill then goes to the president who can either veto or sign the bill. Veto meaning the bill is excused, and signing the bill makes it an official law.