can anyone explain this concept to me?
In a nutshell, a Pythagorean triple $\displaystyle (a,b,c)$ has the property that $\displaystyle a^2+b^2=c^2$
Perhaps the best know method for generating such triples (attributed to Euclid) is to let:
$\displaystyle a=m^2-n^2$
$\displaystyle b=2mn$
$\displaystyle c=m^2+n^2$
where $\displaystyle n<m$ and $\displaystyle m,n\in\mathbb{N}$.
A triple is said to be primitive if $\displaystyle a,b,c$ are co-prime, and requires $\displaystyle m,n$ to be co-prime and $\displaystyle m-n$ is odd.
Pythagorean triple - Wikipedia, the free encyclopedia