(John of the clue crew reporting)  Because the geometric shape here has all right angles, it's called a rectangle; when they're not right angles, it becomes this type of quadrilateral
[DOC] [TLE] How to Prove that a Quadrilateral Is a Rectangle - dummies [PAR] If all angles in a quadrilateral are right angles, then it's a rectangle (reverse of the 
... are right angles  if they are, the fourth one is automatically a right angle as 
well.)