Shoulder pain can occur for many different reasons.
It could be because of a rotator cuff tear or strain, impingement, tendonitis, muscle imbalances or poor posture, amongst other things.
It's easy to injure your shoulder at home, playing sports, weight training in the gym or just by accident if you fall.
My own shoulder pain (which I've completely eliminated now) happened because of a rotator cuff injury which happened while I was at the gym.
I was lifting weights, and must've got something wrong because I felt it "snap".
It didn't hurt immediately, but over the next few hours and days, it developed into a stinging, sharp sensation in the front of my shoulder, and a dull ache on the back.
It hurt a lot, so I obviously wanted to resolve it so I could get back to training, and get back to normal life! I tried asking around my friends to see what their experiences were with shoulder pain, but they didn't really have any better suggestions than, "rest it".
So I went to see a doctor.
He also prescribed rest and some anti-inflammatory medication, and while that did help ease the pain a little, as soon as I stopped taking the pills the pain came right back, so they didn't really solve the core reason for my shoulder pain.
I did some research on the internet, and discovered that you can do physiotherapy at home to treat shoulder pain.
A simple combination of stretches and basic exercises strengthen and heal the shoulder back to normal, and the pain disappears.
The key is to use the right stretches and exercises for your particular type of injury.
If you don't get the right ones, you might end up doing more damage than good - that's why most people go to professional physiotherapists for help with their shoulder pain.