New York (MainStreet) - The federal debt ceilinghas returned. It’s the Michael Bay movie of politics: bad, bald, tired, filled with lots of noise without an ounce of substance.

Starting today, the Treasury Department has hit the limit of its borrowing authority and will begin taking emergency measures to avoid defaulting on its obligations. Last February, Congress enacted a one-year suspension of the debt ceiling, allowing the Treasury department to sell debt as necessary to pay for government spending. That suspension expires today.

On Friday, Treasury Secretary Jack Lew sent a letter to notify Congress of the measures his office will take. With that in mind, here are the answers to a few questions you might have about the debt ceiling, in no particular order.

Are we seriously talking about this again?

Yes.

Seriously?

Yes.

Do we have to?

Sorry.

Why?

Because it matters. Although self-imposed, the debt ceiling is one of the most important issues that Congress will address this year. We owe it to ourselves to understand the bones of what’s happening.

It feels like we’ve been here before.

So many times. During the debt ceiling showdown a year ago, Congress suspended the law altogether. That suspension has run out today, re-imposing the $18.1 trillion cap.

All right… if we have to. So one more time, what is the debt ceiling?

The debt ceiling is a cap on borrowing authority imposed on the Treasury by Congress, most generally expressed as a limit on the sale of treasury bonds (the most common form of direct government borrowing).

So it sets a maximum amount of government debt? That makes sense, right?

Not even a little bit. Government spending drives debt, while the ceiling only caps how much the Treasury can borrow to pay for that.

If I limit my credit card, it stops my ability to build debt. Why doesn’t that work for the government?

For starters because, no matter how many times politicians say otherwise, there is virtually no relationship between a checking account and the federal budget.

More importantly though, it’s because the debt ceiling doesn’t stop Congress from spending. While it caps the Treasury’s ability to borrow and pay the bills, Congress incurs the original liabilities with its spending laws.

So does the debt ceiling do anything to limit government debt?

Not a single thing.

To go back on my word about household budget comparisons, it’s like paying Comcast with a credit card. The debt began once you signed up for a cable package. The credit card just moves that money around.

What’s the point of it then?

In theory, Congress will spend with one eye on the debt ceiling and adjust its activities accordingly. Whatever you think of that theory, the practice hasn’t worked out at all. Unless we’re chalking up repeated near-misses with disaster as a string of successes.

Today the debt ceiling does nothing. It exists as an opportunity for the party out of power to rail against government spending and occasionally try and shake down the White House for some party favors in the process.

What happens if Congress blows this year's deadline?

For a while the Treasury can use “emergency” measures to delay running out of cash. Those measures include drawing down on the currency stabilization fund and halting investments in federal employee pension funds. For more details, see the Treasury’s enumerated list of options at the bottom of Secretary Lews's letter here.

The good news is that these measures will last for quite a while. By cutting corners Treasury can stretch its resources until the end of the year, but by the Congressional Budget Office's estimate, sometime in November or December the government will run out of borrowing authority (and therefore cash). No one knows specifically when, in part, because it will depend on 2014’s tax receipts that have yet to come in.

If that happens, the government will begin defaulting on debts and missing payments. No one knows exactly what happens then, but it will be bad.

So what’s the big deal about paying creditors a few days late?

Defaulting on the debt ceiling would sacrifice the full faith and credit of the United States.

American debt, generally in the form of Treasury bonds, is considered one of the safest investments in the world. That assumption underlies much of the financial system, with banks and investors building entire systems on the principle that money can be stored in treasury bonds with absolute reliability.

If the U.S. Government defaults on its debt that confidence will be shaken. Bonds would become less popular, the government would have to pay higher interest rates to sell them and a banking system built on reliability would suddenly have to call that assumption into question.

It’s difficult to overstate how dangerous that would for both the American and global economies. Missing those payments once means that everyone wakes up in a world where that has become possible. Those payments, once missed, could be missed again. The impact would rock the stock market to its core.

I don’t have any money in the stock market.

Your employer does. Tight markets mean tight credit, fewer loans and huge losses for any business or individual which has tied up cash in the stock market. It’s a cumulative effect which pulls all of the money out of the marketplace like sucking oxygen out of a room, and that leads to layoffs.

This is the ABC version, but this is why a collapsing stock market has such far reaching downstream effects. You don’t need to have money invested in the stock market to lose out big in a crash.

If the debt ceiling is so useless and dangerous, why haven’t we gotten rid of it?

Politics. Some politicians like the opportunity to grandstand about budget deficits, and during politics as usual that has historically worked. The cap would come up, deficit hawks got to talk about irresponsible spending and then Congress passed an increase over several symbolic no votes.

Today an increasingly large and fractious group of legislators on the Right view the debt ceiling as an opportunity to take meaningful action on government spending. The danger is that by attaching conditions to a must-pass bill, this coalition creates a risk that the bill won’t pass. They also encourage opposition from the Democrats, who respond predictably poorly to a strategy that amounts to "give us a legislative victory or we'll trigger a new Depression."

As such, the debt ceiling survives thanks to a combination of legislators who see it as a good opportunity for talking points and others who see it as a chance to extract real policy victories.

Is there any real danger here?

Maybe... It’s borderline unthinkable that Congress would, through inaction, casually place us all in harm’s way. It is also frighteningly possible.

Over the past several years, Congress has continued to push this vote closed and closer to the deadline, with the only breathing room coming after last year’s suspension. The hard-right caucus has raised the most objections to raising the debt ceiling, and they got stronger in the last election. The recent brinksmanship over funding the Department of Homeland Security may give a grim foreshadowing of things to come.

Although the House of Representatives has more than enough votes to raise the debt ceiling, imposition of the Hastert Rule prevents it from coming to a vote unless a majority of Republicans will vote for the bill. As in the past, the likely result is a skin-of-the-teeth bill that relies on support from both parties.

--Written for MainStreet by Eric Reed, a freelance journalist who writes frequently on the subjects of career and travel. You can read more of his work at his website A Wandering Lawyer.