What is a multiple in math?

Multiple means "more than one" and a multiple is any number you can make by multiplying a number by some other number.

More specifically in factoring and integers, multiples are the numbers made by multiplying an integer by other integers (natural numbers, e.g. 1, 2, 3, 4).

Examples: the first few multiples of 3 are 3, 6, 9, 12, 15.
A multiple is a number that can be multiplied by another number to make another number. 4 is a multiple of 8 since 4 can be multiplied by 2 to make 8. 50 is a multiple of 100 since 50*2=100.