Meaning symbol layer

[Aurora_86]

Bye to all,
You know what the symbol means next to the "close" layer?

 

[MassiVonWeizen]

you also find it in your online guide. Anyway:http://help.autodesk.com/view/acd/2017/ita/?guid=guid-b297ebd9-d68c-47e1-87ce-1b3798496599

 

[Aurora_86]

Thank you.