ShaderLab: grouping commands with the Category block

Use the Category block to group commands that set the render state, so that you can “inherit” the grouped rendering state within the block.

For example, 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 might have multiple SubShaders, each of which requires blending set to additive. You can use the Category block for that:

Shader "example" {
Category {
    Blend One One
    SubShader {
        // ...
    }
    SubShader {
        // ...
    }
    // ...
}
}

The Category block does not have an impact on shaderA program that runs on the GPU. More info
See in Glossary performance; it is essentially the same as copy-pasting the code.