The Master Node is a special kind of Node. It is the end point of a Shader Graph that defines the final surface appearance of the shader. Your Shader Graph should always contain one, and only one, Master Node. The Master Node will automatically handle the conversion of a shader between different Scriptable Render Pipelines if there is an available backend.
All Master Nodes share a common set of Controls although certain Master Nodes may include more. See Master Nodes for special Controls on different Master Nodes.