It refers to “Height” of an object. When setting the size of an object such as a collider, enter the numerical value for the direction of Y axis (vertical).
Height mapping refers to a 2D gray-scaled image of the height of terrain with areas in darker shades representing concavities and those in lighter shades representing bumps. It is used to create a terrain.
“Hinge Joint” refers to a function to group together two objects to constrain them to move like they are connected by a hinge.
The connected objects can be freely rotated around the joint as an axis. (However, it can not move in directions other than the axis)
It looks just like opening and closing a door.
“Horizontal” is a visual alignment that goes left to right.
The antonym is “Vertical” that is visual alignment going up to down.
*See the item of “Vertical”.