Or you could say it's dual to money - creating debt creates money, paying debt destroys money. There's literally less money in the world when you make your mortgage payment (bank just sends much of your payment to /dev/null), and there's literally more money in the world when you take a mortgage (bank pulls it out of thin air).
If all debt would be repaid then almost all of the money as we know it today would disappear.
Keeping those two in check is the main goal of any central bank, ever since the gold standard was generally abandoned and money became entirely abstract. In my opinion no one really knows how to do it (although it's been okay-ish so far), the FED for example often uses national unemployment rate to decide how much dollars should be thrown at the system.
It's a very counter intuitive concept that underpins the entire economic system. It was even a subject of a (failed) Swiss referendum recently: https://en.wikipedia.org/wiki/2018_Swiss_sovereign-money_ini...
Mortgages make MBS, mortgaged backed securities, which are traded around. You can buy these, or SLABs, student loan backed securities.
Neither are money. M0 money can only be made by the US Fed. M1 or M2 money can be made by banks out of savings accounts or checking accounts, due to the fractional reserve system.
By lending money to a bank through the savings account mechanism, the bank owes YOU money, because the bank spends roughly 80% of it on other things.
That's why there is a distinction from M0 pure cash, and the M1 or M2 virtual 'nearly money' in the system. I think credit cards are a higher order of money as well...
You need to explain why.
Also, I agree that the person you replied to was oversimplifying.