It is true that a triangle is a figure with three sides and three angles. On the 2-D plane, the sum of these angles is 180°, and the sum of the lengths of the two smallest sides is greater than that of the third side.
Generally, there are three main kinds of triangles by side lengths: 1) An isosceles triangle has two or more congruent sides. 2) An equilateral triangle has three congruent sides and three congruent angles (all 60°). I think this what you're asking about. 3) Finally, a scalene triangle has no congruent sides or angles.
