say what'...Como se dice ....?

Question

I've got questions with the expression "Como se dice'" First what does it mean'. How or when is it used?

I think people say "Como se dice ##### '" Where ##### is a word they don't know. Where they are asking what some word or phrase means. The literal translation seems to be "as it is said".

My second question with the expression is why use "se" in that sentence? According to what I'm studying .... se is not a DOP. It is an IDOP. So my point is that se is uncalled for in this sentence. It should be "Como lo dice." NO'