Have you ever been in math class and had the problem, "What is the least common multiple of x and y?" , and then had to write out every multiple of x and every multiple of y and then go through them to see which ones are the same? Doesn't it take such a long time? Do you ever think "There must be an easier way!" Well, actually, there is. The algorithm is:
GCD = greatest common divisor
But then you also have to figure out the greatest common divisor, which also takes a long time. Good thing computers don't care how long things take! What this program does is it takes the first number you insert and the second number you insert, finds the greatest common divisor of those two numbers, and then does the algorithm x*y/gcd.