Angelina,
Parkinson's disease (PD) is an incurable, progressive, neurological disease. You are correct that the symptoms can be treated ... but the disease can not be cured (yet ... one day .......).
PD symptoms are primarily treated with medication. There are several medications. Different people respond differently to different medications and combinations thereof. So ... no two people will have the same treatment plan. There also is an indication that exercise may slow or stop the progression. More studies are being done in this area.
You ask about tremor. Only 70% of the people with PD have tremor. There are 4 primary symptoms with tremor being one of them. A person can have one of the 4 or any combination thereof. There are many causes of tremor - not just PD. There are blood tests and other diagnostic tools that can be used to help determine the cause of tremors. However, there is no definitive test for PD. It is a process of elimination - ex., EEG to eliminate stroke, MRI to eliminate brain tumor, blood tests, etc - and then clinical observation.
If you or someone you know is concerned about a medical issue, I would encourage you to see a doctor. Obviously there are different types of doctors you would consider based on the symptoms. If tremor is the primary symptom, you may want to see a neurologist. A person with PD would ideally see a neurologist ... or better yet, a movement disorder specialist (MDS) who is a neurologist that specializes in movement disorders such as PD.
I hope this helps. Best of luck!
lizzy4451