The name of the quadrilateral shown in the diagram is Trapezoid.
What is a trapezoid?
A trapezoid is a quadrilateral with at least one pair of parallel sides. The parallel sides are called bases, and the non-parallel sides are called legs.
The height of the trapezoid is the perpendicular distance between the two bases.
In a trapezoid, as the one shown in the diagram, the angles at the bases are equal due their equal length. So this type of trapezoid is called an isosceles trapezoid. The sum of the interior angles of a trapezoid is always 360 degrees.
Thus, the name of the quadrilateral shown in the diagram is Trapezoid.