X, Y, and Z are commonly used variables in mathematics and science to represent unknown values or coordinates. In a two-dimensional space, X typically represents the horizontal axis, while Y represents the vertical axis. When a third dimension is introduced, Z is used to denote depth, allowing for a more comprehensive representation of objects in three-dimensional space. In various fields, such as physics and computer graphics, X, Y, and Z are essential for modeling and analyzing data. They help in plotting graphs, creating simulations, and solving equations, making them fundamental tools for understanding complex systems and relationships.