The shoulder muscles (note plural) are the front, the side and the rear. They have fancier terms which I’m not going to bother with right now.
Suffice to say THERE ARE THREE SEPARATE MUSCLES (once again):
1. Front
2. Side
3. Rear
So common sense would have it, you work out each separate muscle group. Working out only one and neglecting the other two will give you a lopsided or deformed look.
So before you embark on any bodybuilding journey please understand your body and which exercises affect those specific parts of your body and you will have success.