What does the dark triangle, located on the folder icons in Xcode 9, mean?

Question

I use Xcode 9.0. Some folders icons in my Xcode project have dark triangles in bottom left corner - for example, "0. Login", "Frameworks", "Products", "Pods". What does this mean?

Answer 1

Folders without dark triangles exist as a group in your project and also (what is new in Xcode 9) exist as a folder in file structure.

Example: After double-click in your project navigator you can see menu:

For New Group Xcode create group in project navigator and create folder in file structure (in finder) and of cource for New Group without Folder create only group.