This is how I understand it.
Pretend you have a credit card. And this credit card has a limit, we’ll say $1000. This credit card is pretty near maxed out and you don’t really have any cash. You need to buy some stuff soon, and you know that between now and August 2nd you need to buy some things, and you have no choice but to buy them on the credit card. At that point the credit card will be completely maxed out.
This credit card is our debt ceiling. We will hit the limit of our borrowing limit on August 2nd.
Now let’s continue further. We know we have some bills next month, and we also know that we have some cash coming in, but when we look at what we have coming in vs what we have to pay, we don’t have enough to cover it. Let’s just say we know we’ll be short by $100. So now we know ahead of time that we’ll be short, and we only have one real option: call the credit card company and ask them to raise our limit.
This is what the debt ceiling legislation is trying to do: raise our credit limit.