[Q] What does this option do in the scene tab>renderlayers

Hi there,

i was busy make a render when i noticed this option in the layers render under the scene tabs. You can select layer here and update it, but it seems to do double jobs. I can uncheck my layers in the 3d viewport and than under this scene tab reenable them. This seems handy. Byt it understand why there’s a update button and so. I thought that could also check which layers are added per layer render, this doesnt seem possible.

So its about that part under tab where you can make layers for rendering, see attachment

Im not really formiliar with this all, just started using cycles a bit more.
Sorry if its a dumb question