Comment by jjmarr

> A double-entry system is an accounting method that tracks money at both its source and destination.

There's an entire section on double-entry accounting in the article. The tl;dr is that if you take money out of an account, you need to place money in another account and vice versa. So, you have a table called "accounts receivable" which track money the company is owed. If you actually get paid, you remove money from "accounts receivable" and add money to the "cash" account, instead of just increasing the amount of cash you have.

It makes it much more difficult to lose track of money or have it stolen. In a single-entry system, I could receive money from a customer for services owed and just keep it for myself.