sticky bit

as far as i understand, if sticky bit is set on a directory, the files created under tht directory cannot be deleted by ordinary user...

but we can do ths by permission itself,,, tht's assign only read permission to tht dirrectory

wht 's the difference?

ls -l -d /plpl/tmp
drwxrwxrwt   6 root     other      24576 Jul 23 07:31 /plpl/tmp

With this file mode on the tmp directory any user can read,write, and delete any file they
personally create. Depending on the user's umask other users may be able to read or write or execute the file.

I do know what else you are asking, parts of your question are not clear to me.