The SS was formed in 1920 as the saal-schutz, as hall protection. Basically, they protected speakers from attack at party meetings, and beat the crap out of any hecklers that might show up. Under the command of Heinrich Himmler from 1929-1945, the organization became the Schutzstaffel, the protection squad or defence corps, providing security for party meetings and personnel.. During the war, the SS fielded military divisions, fighting along side the regular army, but not under it's command. And of course, the SS had responsibility for carrying out the final solution. For those who don't know what that means, the final solution was the elimination of Jews and other threats to race purity. It's quite possible that the two men in this photograph are war criminals, a nice phrase for genocidal mass murderer.
The famous black uniform with the death's head logo, often seen in movies, was the uniform of the Allgemeine-SS, the political arm of the group. The SS, unlike the SA, and the regular military, took an oath of allegiance to Hitler, rather than to the German state. A sorry example of humanity.