Angles are classified based on their measures. A right angle measures exactly 90 degrees, while an acute angle is less than 90 degrees. An obtuse angle measures more than 90 degrees but less than 180 degrees. A straight angle is exactly 180 degrees, forming a straight line. Another type is the reflex angle, which measures more than 180 degrees but less than 360 degrees. Angles can also be categorized as complementary if their measures add up to 90 degrees, and supplementary if they add up to 180 degrees. Understanding these types helps in various fields, including geometry and trigonometry.