What is the difference between POWs and detainees?

In some sense there is not much difference and in some there are big differences, as a POW the International Red Cross is supposed to have access to them, to include sending care packages and such, also there are minimum standards that are supposed to be met and things you are not allowed to do to them. The detainees held by the US at Gitmo are treated by the rules of the Geneva convention for POW's and in most cases better than required (now I did not say a thing about high profile players that were water boarded, but that is minor compared to how they are treated by their own). Why does the US and Canada give them to the Afghans? One because there is a functioning (sort of) government in Afghanistan, two, if we kept them it would be another reason for terrorist attacks, and three if there were accusations of torture we would have to spend millions of dollars on court proceedings like we did a short while back when a captured terrorist accused the Navy SEALS of giving him a fat lip.