A right angle is defined as an angle that measures 90 degrees. When two lines intersect to form a right angle, they are said to be perpendicular to each other. When two lines intersect at a right angle and form a corner, that corner is typically referred to as a square corner.
While a right angle will always form a square corner, not all square corners are formed by right angles. It is possible to have a square corner formed by two lines that intersect at an angle other than 90 degrees. However, this is not typical and most square corners are formed by right angles.