G.C.F is called greatest common factor.It is the number that divides both the numbers. For example GCF of 2 ad 4 is 2.
GCF of 6 and 9 is 3.
GCF of 8 and 25 is 1. If there is no common number that divides both the numbers then in that case GCF=1.
The statement The gcf of two numbers is equal to the lesser of the numbers is not always but sometimes true.