Is 1/3 greater than 1/8

A fraction is a part of something. The bottom part the, divisor or denominator, tells you how many parts you have divided it into. The top bit tells you how many parts you take. The numerator.

1/3 tells you have divided something into 3 equal parts and you have taken one of them.

1/8 tells you have divided something into 8 equal parts and you have taken one of them.

So think it like this

would you like to have a cake into 3 pieces or 8 pieces