A Geometry Shader is a type of shader used in computer graphics, specifically within the graphics pipeline. It processes geometric primitives like points, lines, and triangles, allowing for the creation of new geometry from existing shapes. This shader can add, modify, or remove vertices, enabling effects such as dynamic tessellation or creating complex shapes without needing additional geometry data. Geometry shaders are often used in conjunction with other shaders, such as Vertex Shaders and Fragment Shaders, to enhance visual effects in 3D rendering. They provide flexibility in rendering techniques, making them valuable in applications like video games and simulations where detailed graphics are essential.