What does TYPE SAFE mean?

"Douglas Lewit [email protected] [ocaml_beginners]" <[email protected]> Sat, 13 Feb 2016 01:01:31 -0600
Newsgroups gmane.comp.lang.ocaml.beginners
Message-ID <CAM0XMJR4JiMfK7ZiSa__8deo+nEPbx=+6WB3EEnZYu_qTJwknA@mail.gmail.com>
What do people mean when they say that Ocaml is a "type safe" language?

Thanks,

Douglas.