: DirectX 10 replaced separate vertex and pixel shaders with a more flexible "unified" model that could handle any task.
: Positioned between vertex and pixel shaders, this allows GPUs to create new geometry on the fly, which is particularly useful for particle systems, billboards, and sprites. Directx 10
Today, DirectX 10 is considered legacy technology, and support has largely ended for modern titles: DirectX 10 Tutorials - Taking Initiative : DirectX 10 replaced separate vertex and pixel