Sealant is a flexible, adhesive material used to seal gaps, joints, and seams in construction and repair projects. It provides a watertight and airtight barrier, preventing moisture, air, and contaminants from penetrating surfaces. Sealants are available in various formulations, including silicone, acrylic, and polyurethane, each designed for specific applications. They are crucial for maintaining the integrity and longevity of structures, both indoors and outdoors.