Factors are the numbers you multiply together to get another number. When you find the factors of two or more numbers, and then find some factors are the same ("common"), then they are the "common factors"
Example: 12 and 30
• The factors of 12 are: 1, 2, 3, 4, 6 and 12
• The factors of 30 are: 1, 2, 3, 5, 6, 10, 15 and 30
So the common factors of 12 and 30 are: 1, 2, 3 and 6
-Hope this helped.