Annual Percentage Yield (APY) is the annual percentage rate of investment returns including compounding interest. This generally results in a higher advertised rate, as interest compounded over the investment period results in a higher percentage rate (than interest without compounding). We use this to advertise what your annual investment return could be over a given time period where your assets remain in Earn (ie, assuming your investment amount does not change after the initial investment is made).
Rewards Per Year (RPY) is the annual percentage rate excluding compounding interest. This generally results in a lower advertised rate, as it only considers the initial investment amount and not compounding interest that applies over time. We use this to calculate your next expected payout (noting that the actual value of the payout may fluctuate due to fluctuations in the market value of the particular cryptocurrency).