A triangle.
There is no special name: they are polygons, as are shapes with 3 or 3 million sides.
Most shapes do not have equal sides. In nature, shapes with equal sides are the exception rather than the rule.
Polygons are shapes with 3 or more sides
Triangles
Triangles have 3 sides.
A triangle
A Triangle
It is a polygon that has 3 or more sides
Triangles
a triangle
The shape that has not got equal side is a rectangle
They are polyhedra.