This code defines a function called multiply that takes two...

This code defines a function called multiply that takes two integer parameters a and b. It calculates the product of a and b using recursion.

The line "return a + multiply(a, b-1);" recursively calls the multiply function with the same value of 'a' and decremented value of 'b'. This continues until b becomes 1, at which point it returns the value of 'a'. The function effectively multiplies 'a' by 'b' by repeatedly adding 'a' to itself 'b' times.