How bill become a law?

"If a bill has passed in both the U. S. House of Representatives and the U. S. Senate and has been approved by the President, or if a presidential veto has been overridden, the bill becomes a law and is enforced by the government."

so first,

1. its an idea or known as a bill

2. both the U. S. House of Representatives and the U. S. Senate then debate on this

3. than it is passed to the president where he can either sign or veto

4. even if he vetos it can be over ridden but if the court decides its constitution the bill becomes a law

I don't understand the question ... How bill become a law ... like how did paying a bill (food, light, water, heater) become a law?