what is LCF and HCM?

I think you mean LCM and HCF

LCM = lowest common multiple (or least common multiple)

HCF = highest common factor

 

So, the LCM of 4 and 6, say is 12,  because multiples of 6 are 6, 12, 18 ... and multiples of 4 are 4, 8, 12, 16 ...

The lowest one in common is 12.

 

The HCF of 8 and 12 is 4 because the factors of 8 are 1, 2, 4, 8 and the factors of 12 are 1, 2, 3, 4, 6, 12.

The highest one in common is 4.