A triangle has one angle of 90 °, what is this type of triangles called?

An angle of 90⁰ is called a right angle, and a triangle with this angle is right-angled. The two remaining angles of such a triangle together are 90⁰:
180⁰ – 90⁰ = 90⁰;
Moreover, if the acute angles of such a triangle are equal to each other, this is a right-angled isosceles triangle.
The sides of the triangle adjacent to the right angle are called legs, and the hypotenuse is the side opposite the right angle.