ShaderLab includes a number of “fixed-function style” commands that allow you to write shadersA program that runs on the GPU. More info
See in Glossary without using any HLSL code.
Note: These commands are legacy, and are documented for backwards compatibility only. If your Shader objectAn instance of the Shader class, a Shader object is container for shader programs and GPU instructions, and information that tells Unity how to use them. Use them with materials to determine the appearance of your scene. More info
See in Glossary source file includes HLSL code, Unity ignores these commands completely. If your shader source file does not include HLSL code, Unity compiles these commands into regular shader programs on import.