A triangle is a type of polygon with three sides, and the two sides are joined end to end, called the vertex of the triangle. The sum of all three interior angles is equal to 180 degrees.

Based on the length of the sides, triangles are classified into three categories: Scalene Triangle(no sides equal), Isosceles Triangle(two sides are equal), Equilateral Triangle(3sides are equal).

Based on the measurement of the angles, triangles are classified into three categories: Acute Angle Triangle(3-angles is < 90°), Right Angle Triangle(is equal to 90°), Obtuse Angle Triangle(one of angle is > 90°).

Explanation: The images showcase various types of triangles and their corresponding angles.