What Does the Equation, (1 + R/m)^m - 1,calculate

What does the equation, (1 + r/m) ^m - 1,calculate?

A) Compound interest rate over t periods where r is the effective simple interest rate
B) Compound interest rate over t periods where r is the number of compounding periods
C) The number of compounding periods over t years where r is the effective simple interest rate
D) Effective simple interest rate over t periods where r is the compound interest rate