The Z-coordinate is a value used in a three-dimensional coordinate system to represent the position of a point along the vertical axis. In this system, points are defined by three coordinates: X, Y, and Z. The X and Y coordinates indicate the horizontal position, while the Z coordinate shows how high or low the point is relative to a defined plane, often referred to as the XY plane. In practical applications, the Z-coordinate is essential in fields like computer graphics, engineering, and architecture. It helps create realistic 3D models and simulations by allowing objects to be placed at various heights, enhancing depth perception and spatial understanding in designs.