This shader is Vertex-Lit, which is one of the simplest shaders. All lights shining on it are rendered in a single pass and calculated at vertices only.
Because it is vertex-lit, it won’t display any pixel-based rendering effects, such as light cookies, normal mapping, or shadows. This shader is also much more sensitive to tesselation of the models. If you put a point light very close to a cube using this shader, the light will only be calculated at the corners. Pixel-lit shaders are much more effective at creating a nice round highlight, independent of tesselation. If that’s an effect you want, you may consider using a pixel-lit shader or increase tesselation of the objects instead.
Generally, this shader is very cheap to render. For more details, please view the Shader Peformance page.