Congress failed to pass a spending bill by Friday at midnight, triggering a shutdown of the federal government.

The move has big repercussions for America. US troops will continue their duties, and post will get delivered, but almost half of the two million civilian federal workers would be barred from doing their jobs.

Here's a look at what it means to shut down the government.

Intelligence work will be scaled down

The workforce at the 17 US intelligence agencies will be pared down significantly.

An official said employees who are considered essential and have to work will do so with no expectation of a regular pay cheque.

While they can be ordered to stay on the job, federal workers can't be paid for days worked during a shutdown. In the past, however, they have been paid retroactively even if they were told to stay at home.

National Parks and museums

The Smithsonian museums in Washington, and the National Zoo, which are huge tourist attractions, will close from Monday if the shutdown continues.