GCF stands for Greatest Common Factor. A factor of a number is a whole number that goes evenly into the number by multiplying it by another whole number factor.
So 16 has the following factors: 1, 2, 4, 8, 16; they all go evenly into 16.
60 has the following factors: 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60.
Now the GCF of both 16 and 60 is the largest (greatest) factor that they both have in common. That number is 4 that they both have in common.
