There are a few different types of mats that can be used in front of a door. The most common type is a doormat, which is typically made of materials like coir or rubber and helps to remove dirt and debris from shoes before entering the home. Other types of mats that can be used inside in front of a door include floor mats, area rugs, or even welcome mats. Each type of mat has its own benefits and should be chosen based on the specific needs of the space.