Emacs buffers don't need to be associated with open files.
Basically menus, project trees, terminal tabs, etc. Are all just text buffers. So you can navigate them like they were a file opened in a regular text buffer.
The netrw plugin that comes with the default installation of vim on many distros allows you to navigate the directory listing like a file, but it won't let you edit the text. The terminal buffer is similar, but you have to enter a special normal mode (ctrl-w N) in order to navigate the scrollback like a conventional buffer, but you can't change the contents of the buffer.
Basically menus, project trees, terminal tabs, etc. Are all just text buffers. So you can navigate them like they were a file opened in a regular text buffer.