A coordinate system is used for the unique description of points with the help of numbers, the coordinates. The best known coordinate system is the Cartesian coordinate system. It can be two- or three-dimensional. A 3D, i.e. three-dimensional coordinate system makes it possible to represent spatial structures in the three dimensions of height, length and width. It is also called a spatial coordinate system. It is therefore an extension of the two-dimensional coordinate system by another axis and dimension. The axes in the coordinate system are described with the letters x,y and if necessary z. They stand orthogonally to each other and are in the same direction. They are orthogonal to each other and meet at the zero point. A subdivision takes place along the axes, with the two-dimensional coordinate system in quadrants, with the three-dimensional coordinate system in octants. The two-dimensional coordinate system serves only for the work in the plane, for the work in the space the third dimension is indispensable. In the 3D coordinate system, for example, it is possible to represent skewed straight lines, i.e. straight lines that are not parallel, but do not intersect each other either. In the 2D coordinate system this is impossible. There are also subtypes of the coordinate system that are used particularly in measurement technology, such as spherical coordinate systems.