The differences are as follows:

In geometry, "midline" refers to the connecting line between a vertex of a triangle and the midpoint of its opposite side.

"Middle vertical line" refers to a straight line passing through the midpoint of a line segment and perpendicular to this line segment.

"Height" refers to the distance from the apex of a triangle or parallelogram to the opposite side, the distance between the upper and lower bottom surfaces of a trapezoid, the distance from the apex of a pyramid or cone to the bottom surface, and the distance between the upper and lower bottom surfaces of a frustum or frustum.