A tooth cavity, also known as dental caries or tooth decay, is a hole that forms in your tooth due to the breakdown of tooth enamel caused by bacteria. These bacteria produce acids when they consume sugars and starches, eroding the enamel and creating cavities. Early signs include sensitivity to sweets, hot or cold foods, and visible holes in the teeth, while prevention includes good oral hygiene, a balanced diet, and regular dental check-ups. Prompt treatment is essential to avoid further dental issues.