Unity Editor - What grey icon against a folder means?

Hi. I’ve restored my Unity project from Unity Collaboration and for whatever reason one folder has a grey icon which I’m not sure of what it does. Pretty sure this is something related to Unity Collaboration but I’m unsure. Anyone knows what it means (see image bellow)?

177460-icon.png

I know this is an old question, but Just wanted to answer, since I was searching for similar thing and Figured someone might come across this.

Basically there is this thing .CollabIgnore, there are names written in this file that should be ignored when sharing. This symbol means it’s one of those files, either change the name from Build or remove that name from that file.