Ulcers occur due to a variety of factors, primarily involving an imbalance between stomach acid and the protective mechanisms of the stomach lining. Common causes include infection with Helicobacter pylori bacteria, prolonged use of nonsteroidal anti-inflammatory drugs (NSAIDs), excessive alcohol consumption, and stress. Lifestyle factors, such as diet and smoking, can also contribute to ulcer development. If not treated, ulcers can lead to more severe complications, making it important to seek medical advice if symptoms arise.