Pipe fittings are components used in plumbing and piping systems to connect pipes and other components. They include tees, ELLS, ELBOWS, and sleeves. Tees are T-shaped pieces that allow for the connection of three pipes or other components. ELLS are L-shaped pieces that allow for the connection of two pipes or other components. ELBOWS are curved pieces that allow for the connection of two pipes or other components at an angle. Sleeves are cylindrical pieces that allow for the connection of two pipes or other components.