HELP!! A question about the housing bill Trump will not sign.

[AverageOldGuy]

By now we all have heard that Trump says he will not sign the housing bill that passed House and Senate by big margins until his "SAVE Act" is passed. I'm not certain what can happen.

As I understand it, when both Houses of Congress pass a bill, it goes to the President for signature, which means:

1. President signs it, it becomes law.
2. President vetoes it; bill goes back to Congress to override/fail to override the veto.
3. If President doesn't sign or veto in 10 days, the bill becomes law.

It's #3 I'm not certain about -- is it that simple? I'll use the Google machine to see what I can find but would appreciate one of the many brilliant DUers to explain this to us.