Two fractions 
and 
both represent the same number, one half.
The first fraction is preferred, however, because it uses the
smallest possible numbers on top and bottom, which makes it easier for
people to figure out what it means. Finding a fraction with the
smallest possible numerator and denominator
is called reducing a fraction.
The idea in reducing fractions is that a number, divided by itself,
is one. So we try to find common factors in the numerator and
denominator, and then we eliminate them. That is, for
(knowing that 4=2*2 and 6 = 2*3), we have:
