The triangle is a 3 sided polygon. Triangles are classified by the lengths of their sides. Equilateral triangles have 3 sides all equal in length. The triangle differs slightly from the isosceles and scalene triangles because they have unequal sides and the triangle sides are equal. Look around and you can find a triangle shape in virtually everything, including this triangle ladder. Visit wikipedia.org triangle (geometry) for more detailed information about the triangle shape.