The GCM, or Greatest common multiple, and LCM, or Least common
multiple, are opposites of each other. These terms are used when
you are comparing two numbers, or searching for factors of two numbers.
GCM is not usually discussed, but rather the GCF, or greatest common
factor. This is the largest number that can be divided into evenly two
numbers. For example: If I was comparing 24 and 36, the GCF between the
two of them would be 12. It is the largest factor that can be divided
evenly into both of them (into 24 twice, and 36 three times).