ELI5: Explain Like I'm 5

double-entry accounting

Double-entry accounting is like a big checkbook. When you get money from someone, you write it down on one side of the book. Then you write down what you spent the money on on the other side. That way, you can keep track of exactly how much money you have and where it's going. It's like keeping a record of every financial transaction you make, so you can make sure everything adds up.