What is the fundamental difference between APR $($Average Percentage Rate$)$ and APY $($Average Percentage Yield$)?$

APY is calculated using simple interests, while APR is calculated using compound interests.

APR calculates monthly interests, while APY calculates quarterly interests.

APR is used by the goverment, while APY is used by private companies.

APR is calculated using simple interests, while APY is calculated using compound interests,