Mouth ulcers, also known as canker sores, are common oral lesions that cause discomfort and pain. They appear as small, round, or oval sores inside the mouth, including the cheeks, lips, tongue, and gums. While mouth ulcers are not contagious, they can be bothersome, affecting eating, drinking, and speaking. Understanding their causes, treatment options, and preventive measures can help manage and reduce their occurrence.