How Do I List Subfolders in Linux?

How do I list all sub folders?

If you name one or more directories on the command line, ls will list each one. The -R (uppercase R) option lists all subdirectories, recursively.

How do I see folder structures in Linux?

You need to use command called tree. It will list contents of directories in a tree-like format. It is a recursive directory listing program that produces a depth indented listing of files. When directory arguments are given, tree lists all the files and/or directories found in the given directories each in turn.