Dental impressions are molds created from the shape of a person's teeth and gums. They are used by dentists to design custom dental appliances, such as crowns, bridges, and dentures. The process involves using a soft material that hardens to capture the details of the mouth. There are two main types of dental impressions: traditional and digital. Traditional impressions use a tray filled with a pliable material, while digital impressions utilize a camera to capture 3D images. Both methods help ensure that dental restorations fit accurately and comfortably in the patient's mouth.