There are a number of informal colloquial words that are used as placeholders when you can't remember the name of a thing: "whatsis," "whatsit," "whosy-whatsis," "gadget," "widget," "thing-um-a-bob," "thingy."

What does it ...is a phrase used before the thing/object being asked about. What does it do? What does it mean? . ..

I think the question you're referring to is "What does it mean?" In spoken English this question sometimes sounds like "What's it mean?" because the first part of the word "does" gets swallowed. In writing we do not normally use a contraction for "what does", but in speech we can. In writing "what's" usually refers to "what is" or "what has".