What's the difference between "what are you waiting for" and "what do you waiting for"?
"What do you waiting for?" is ungrammatical; however, "What do you wait for?" is okay.
"What are you waiting for?" is present tense – if someone asks me that question, they are assuming I am waiting for something, and are asking what it is I am waiting for:
What are you waiting for?
I am waiting for the train to come by.
"What do you wait for?" is asking about something that is ongoing:
Every day I see you standing here, as if you're waiting for something. What do you wait for?
I wait for the train to pass by.
One other thing: "What are you waiting for?" is sometimes used as a rhetorical question, asking essentially the same thing as, "Why are you just standing there?"
Billy, I need you to go out and rake the leaves.
Billy [not moving]: "Okay."
Well, what are you waiting for?
The phrase "What do you wait for?" would not be used in this context.