A Vertex Shader is a small program that runs on the graphics card, specifically designed to process each vertex of a 3D model. It takes input data, such as the position, color, and texture coordinates of the vertices, and transforms them into a format suitable for rendering. This transformation often involves calculations based on the camera's perspective and the model's position in the scene. Once the Vertex Shader has processed the vertices, it passes the data to the next stage in the graphics pipeline, which is typically the Fragment Shader. This allows for detailed rendering of the model, including lighting and texture effects, ultimately creating the final image you see on the screen.