Beauty Passes provide a rendered view of different aspects lighting the scene such as shadows, highlights, reflections, illumination, and color. Beauty passes are rendered together with the main beauty pass. Each one of these requires its own frame buffer that needs to be stored in addition to the main frame buffer.
INformatION regardIng to some of the passes
You can choose the pass type from the Beauty Pass menu. Do not check all of them because both the waste of time and the size of the project. In addition, since Octane renders each pass individually, it will be the most efficient way to select the right pass you need.
Raw rendering allows more control over the final look in post-production. If you check the Raw button, you will get the image similar to beauty render. Since you specify the render output format from the file and format field most of the time, you can turn this option off.
This pass contains all direct light shadows that are calculated on the first path bounce. The pass includes sun light provided by the Octane Daylight Environment. The Shadow pass excludes the sky light (a.k.a Octane Sun+Sky environment) or texture environment if the texture environment does not consist of an image. If the environment contains a sky light or texture environment that is contributed by an image texture, the pass takes the value in the Environment's Importance Sampling attribute into account. Make sure to enable Importance Sampling in the Environment to include the sky light or texture environment in the Shadow pass. You can go to this and this section for "Importance Sampling" explanations.
This pass is used to observe the rendering progress through the noise estimate value when Adaptive Sampling is used with the Path Tracing or Direct Light Kernels. A pixel is treated as "noisy" if the noise level is higher than the given threshold. When the noise estimate for a pixel becomes less than the given noise threshold, the value is a green color which also switches off sampling for that pixel and tells the rendering process to concentrate on other areas. This pass shows which pixels have noise lowered down to the specified noise threshold as the rendering progresses. You can go to here for detailed explanation.