Recently, I was reviewing my investments and wondered: what is APR really, and why do people always talk about APY? Turns out, these two terms are super important if you want to understand how much money you'll earn or spend on your financial operations.

Okay, let's start with the basics. APR, which is the APR in its simplest form, is the annual percentage rate calculated on the initial principal. It's like saying: I will invest $100 and will earn $10 interest per year. That's APR. You see it a lot in credit cards, personal loans, and mortgages. The problem is that it only looks at the principal, not what happens afterward with the interest you've already earned.

Now, APY is a completely different story. This one takes into account compound interest, meaning when interest generates more interest. Imagine that the same $100 is compounded monthly. In the first month, you earn interest on $100, but in the second month, you earn interest on $100 plus what you've already earned. It's like your money multiplies itself. That's why APY is almost always higher than APR.

The key difference between these two concepts is precisely that: APR does not include compound interest, while APY does. If you invest in a bank account or crypto staking, you need to look at the APY to really know how much you'll earn. If you only look at the APR, you'll be missing out on actual gains.

Let me give you an example to make it clearer. A credit card says: 15% APR annually. That means you'll pay 15% on what you owe, period. But if you see an investment account offering 15% APY, that's different because the interest is compounded regularly, sometimes even daily. So, at the end of the year, you'll have earned more than with a simple 15%.

What I've learned is that when making financial decisions, you can't just look at the APR number. You need to understand what APR means in your specific context and compare it with the APY if compound interest is involved. In the long run, that difference can be quite significant to your overall profitability. So next time you see an investment, ask yourself: is it APR or APY? That question can make a big difference in your final earnings.