Have you seen the Futurama episode where Fry goes to a bank where he left 93 cents in in 2000 and that grew to 4.3 billion dollars in 3000? That's compound interest. Except on lewdcorner it compounds daily instead of yearly, so it's 365 times faster and most people are going to put in more then 0.93 lewdcoins into their bank
Actual explanation if someone actually wants it: Compound interest is when you're earning interest not just on the initial investment, but on the interest you're earning on that investment as well. It's a very powerful force that over time has a huge effect on the value of the investment. As an example, if you invested 1000 lewdcoins into the bank, at 2% interest per day if there was not compound interest you'd gain 20 lewdcoins back every day, and you'd double your lewdcoins to 2000 in 50 days. With 2% compounding interest you'd in theory instead double your coins in 35 days (in practice, it'd be somewhat different because you can't get fractions of lewdcoins so it'd depend on how the system rounds your interest)
Saving 15 days, pretty good, but where it gets more powerful is continuing forward, in another 50 days, so 100 days total, the non compounding investment is at 3000 coins, but the compounding investment doubled AGAIN from 2000 to 4000 at 70 days, then doubled again to 8000 coins at 105 days. At this point the fact that that 2% is compounding has meant the investment has more then doubled in value compared to how much it'd be worth if it wasn't compounding. As you continue to go forward it'd double again and again, gaining a huge amount of value over time.
This is why investing money for your retirement when you're younger is soooooooo much better then doing it when you're older. The power of compound interest over time gets fairly ridiculous.