The Queue tag tells Unity which render queue to use for geometry that it renders. The render queue is one of the factors that determines the order that Unity renders geometry in.
You can use the Queue tag in two ways: you can tell Unity to use a named render queue, or an unnamed render queue that it renders after a named render queue.
This example code creates a SubShader that renders geometry as part of the Transparent render queue:
Shader "ExampleShader" {
SubShader {
Tags { "Queue" = "Transparent" }
Pass {
…
}
}
}
This example code creates a SubShader that renders geometry in an unnamed queue, after the Geometry queue.
Shader "ExampleShader" {
SubShader {
Tags { "Queue" = "Geometry+1" }
Pass {
…
}
}
}