There are 4 types of triangle. They all have 3 sides and are polygons.
Equilateral triangles have 3 equal sides and 3 equal angles of 60°
Isosceles triangles have 2 equal sides and 2 equal angles.
1 of the angles is a right angle (90°) in right-angled triangles.
Scalene triangles have no equal sides and no equal angles.