A 90-degree angle is a type of angle that measures exactly 90 degrees. It is one of the most common angles in geometry and is often referred to as a right angle. A right angle can be found in various shapes, such as squares and rectangles, where the corners form 90-degree angles. In practical applications, 90-degree angles are essential in construction and design, ensuring structures are level and stable. Tools like the carpenter's square are used to create and measure right angles, helping builders achieve accuracy in their work.