The plane parallel to LE is the plane BGDH.
Two planes are considered parallel when they do not intersect, meaning they do not share any common points and any straight line between them are perpendicular to both planes.
In other words, if you extended both planes indefinitely, they would never cross each other. In the given figure, line LH is shown to be at right angle with line LE and also to line HB this implies line LH is perpendicular to both LE and HB. This places the planes LE and HB in parallel positions.
Therefore, since the lines of the plane BGDH is placed perpendicular to that of LE, then they are parallel planes.