Shoulder

Best is to see some videos, and this is probably the best series I found, probably best seen in this order...:

1. Rotator calf muscles Although he is not talking about the other structures in detail, you can see basically how the shoulder holds to your body. He touches on other muscles that are described on the next video. See also the exercise video below who explains this really simply.
2. Large shoulder muscles. Want more details, names, etc. Check this.
3. You can quickly go through this one where he talks about the scapula/bones. No need to know so much detail to get the sense of how the shoulder works.
4. Glenohumeral joint: bones/tendons and movements/actions names.

If you are looking how to solve your shoulder pain (mine, which may have nothing to do with yours) got solved doing this. The video is good even to explain the structure of the shoulder really clearly. This guy is actually talks a lot but he is good also (actually is the first one I saw). The last exercise works like a charm. He has a second video and a 3rd one that I got to try.