system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When you deposit to a bank, does the bank just store the money

So let me explain in more detail here. When it comes to a bank accepting a cash deposit to your account and you get said amount accredited to your account what does the bank do with said money. It's not like they would want to keep billions and billions of dollars of cash stored somewhere because it was deposited. How does that all work?
gpt
The way modern banking works is heavily reliant on what we call 'fractional reserve banking'. When you deposit money in the bank, a portion of that money (say, 10%) is set aside and actually kept in the bank. The other 90% of the money is made available for loans from the bank. 

That is, effectively, what a bank's main business is. In return for putting your money in the bank, you get some money as interest, and the bank uses your money to give out loans, which will in turn be repaid to the bank with more interest.