Pork shoulder roast can be labeled several different ways at the grocery store. Boston Butt, and and pork Butt all refer to cuts of meat that all come from the shoulder of the pig. They can be packaged bone-in or boneless. A picnic shoulder is taken from a section lower than the shoulder. And a pork loin roast is cut from a different section and is a much leaner cut of meat. For a visual, I like this Pork Cuts 101 diagram from Smithfield