The chooser shows a list of files with icons. Files which appear to be media files, or are too large will be disabled and not selectable. Touch a folder to change folder, or a file to open a file. Hidden files beginning with a '.' will not appear.
The parent folder, if it exists, will appear first in the list. Touch
that folder to move up the directory tree. If a folder is not
accessible, the chooser will show the parent folder, if it exists, and
the external storage folder (/storage/emulated/0).