An obtuse triangle is a type of triangle that has one angle measuring more than 90 degrees. This means that the largest angle in the triangle is obtuse, while the other two angles must be acute, each measuring less than 90 degrees. The sum of all angles in any triangle, including an obtuse triangle, is always 180 degrees. In an obtuse triangle, the side opposite the obtuse angle is the longest side. This characteristic helps in identifying the triangle's type when given its angles. Obtuse triangles can be found in various real-world applications, such as architecture and design.