ShaderLab

ShaderLab is a declarative language that you use in shaderA program that runs on the GPU. More info
See in Glossary source files. It uses a nested-braces syntax to describe a 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.

There are many things that you can define in ShaderLabUnity’s language for defining the structure of Shader objects. More info
See in Glossary, but the most common are:

• Defining the overall structure of the Shader object. See ShaderLab: creating a Shader, ShaderLab: creating a SubShader, and ShaderLab: creating a Pass.
• Using code blocks to add shader programs written in HLSL. See ShaderLab: adding shader programs.
• Using commands to set the render state of the GPU before it executes a shader program, or to perform an operation involving another Pass. See ShaderLab: commands.
• Exposing properties from your shader code so you can edit them in the material InspectorA Unity window that displays information about the currently selected GameObject, asset or project settings, allowing you to inspect and edit the values. More info
  See in Glossary and save as part of a material asset. See ShaderLab: defining material properties.
• Specifying package requirements for SubShaders and Passes. This enables Unity to run certain SubShaders and Passes only when particular packages are installed in the Unity project. See ShaderLab: specifying package requirements.
• Defining fallback behavior for when Unity cannot run any of the SubShaders with a Shader object on the current hardware. See ShaderLab: assigning a fallback.