What do the supercharges in extended supersymmetry do?
In $N=1$ supersymmetry there are a certain number of fermions and and equal number of bosons. You can transform all fermions to the bosons (and vice versa) in a 1 to 1 fashion using a single supercharge, $Q$.
So what happens when you have, for example, $N=2$ supersymmetry with 8 supercharges? Since $Q$ is a generator of supersymmetry transformations, is it a linear combination of these supercharges that act on the particles? In which case could one particle be acted on by two separate linear combinations of $Q$? Or is it strictly one linear combination of $Q$ per fermion/boson?
Also, what does $N$ mean physically? What difference does $N=2$ have to $N=1$ other than more supercharges? Or is that the only difference between the two theories?