Parkinson's disease is a progressive neurological disorder that primarily affects movement. It occurs when nerve cells in the brain, particularly those producing the chemical dopamine, begin to deteriorate. This leads to symptoms such as tremors, stiffness, and difficulty with balance and coordination. While the exact cause of Parkinson's disease is unknown, it is believed to involve a combination of genetic and environmental factors. Diagnosis typically involves a medical history review and neurological examination. Although there is no cure, treatments like medication and therapy can help manage symptoms and improve quality of life.