Fathoming the quagmire of modes of files and their directories together with ownerships, sticky bits, and extended attributes can be confusing. TMI spells it all out in plain language.
TMI ('too much information') provides more information than any other utility of its kind. All data is easily exportable in plain text format and picked up with ease by the ACP text editor Rixedit.
If you find it a bit difficult to understand why some files can go some places but not others, TMI might be a good place to start.
