Question: what is a common factor of 6 and 8?
Answer: Factor of 6 = 1, 2, 3 and 6. Factor of 8 = 1, 2, 4 and 8. Therefore, common factors of 6 and 8 = 1 and 2. [It can easily be shown that each common factor (1 and 2) divides the given numbers 6 and 8 exactly].