Multiples are numbers that a lower number goes into. Like multiples of 4 are 4, 8, 12, 16, 20, 4, 28, 32, 36 and so on. The multiples of a whole number are found by taking the product of any counting number and that whole number. The least common multiple of a set of whole numbers is the smallest multiple common to all whole numbers in the set.
The LCM of two numbers is the smallest number that can be divided by both. It can be used to find the lowest common denominator when you add or subtract fractions.
Multiples of a number are found by multiplying that number by 1, 2, 3, 4, 5, etc.