Factoring is the process of finding the factors that are multiplied to reach a certain number. With actual numbers, it is a fairly simple process, but it becomes more difficult when factoring an equation with variables instead of numbers.
For instance, finding the factors of a number like 10 is fairly simple. For instance, all the factors of 10 are 1 and 10, 2 and 5, -1 and -10 and -2 and -5 because 1 times 10 is equal to 10, as is 2 times 5, and so on. The process is more difficult when factoring a quadratic such as x squared plus 5x plus 6, where the factors are (x plus 2) and (x plus 3).
If a number only has two factors, one and itself, it is considered a prime number. An example of a prime number is 11, which can only be evenly divided by one and 11.