I think most of us know a pork butt is not a butt - it's a shoulder. As I recall, this was discussed in a thread here maybe a month ago? The consensus was - a pork shoulder is considered to be the entire upper "arm" from the top of the shoulder almost at the neck to just above the elbow and it's long and huge. It's rarely sold that way. If you cut it in half at the joint, which is how it's usually sold, the top half is the boston butt and is more round shaped and typically doesn't include skin. The bottom half is a bit elongated since it holds a large portion of the "arm" and typically includes skin. It's usually described with the word "picnic." So it's helpful to use "picnic" or "boston" when referring to pork shoulder cuts. But sometimes stores will just say "shoulder" and it's up to you to look at it and figure out what it is, but I find it's usually a picnic when it's just labeled shoulder. Once I saw some pork in the Safeway labelled as "shoulder." I studied it. I realized they took a 9 lb boston butt which was nearing the sell by date and sliced it into thirds to make it more appealing to buyers. The center third made up a 5 lb part, while the other two pieces in different packages made up two 2 lb parts of the boston. The tiger muscle was intact on that center cut, so yeah, I grabbed that, smoked it low and slow and it came out all jiggly and amazing.