Arthritis is a general term for a group of more than 100 inflammatory joint diseases that can cause pain, swelling, and stiffness in the joints. The most common types are osteoarthritis, which results from wear and tear, and rheumatoid arthritis, an autoimmune condition where the immune system attacks the joints. Symptoms can vary in severity and may lead to decreased mobility and quality of life. Treatment often includes medication, physical therapy, and lifestyle changes to manage symptoms and improve joint function.