"How about" vs. "What about"

I think how about is used when suggesting an idea, which could be answered or not, whereas what about requires answering, but I'm not very sure..

"What about ..." is usually a way to bring an objection or potential obstacle into consideration in my experience, whereas "how about ..." expands, rather than restricts, the possibilities."

This is a very good way to describe it. Here are some examples:

Andy: "I'm bored. There's nothing to do." Danny: "How about we go see a movie?"

Andy: "I'm bored. Let's go see a movie." Danny: "What about our exams tomorrow?"

In the first example, Danny expands the possibilities: Andy thought there was nothing to do, but Danny reminded him that they could see a movie.

In the second example, Danny limited the possibilities: Andy wanted to see a movie, but Danny reminded him that they had to study for their exams.

On a side note, "what about" cannot take a sentence. "What about we see a movie?" is wrong. You can say, however "What about seeing a movie?" or "What about a movie?"

From what I´ve learned teaching English, and what I´ve seen in most books, the difference is that we use WHAT ABOUT + noun, and HOW ABOUT + verb. It´s a pretty simple explanation, but that´s how it´s being taught in schools in Brazil.

I was just asked this question by a friend of mine, and after pausing to analyze my native intuition, I googled to see if anyone had done a more thorough analysis.

The answers here helped solidify my sense of the difference, but none of them entirely captured the difference that I perceive, though several touched on it.

It seems to me that, while there is much similarity and overlap between these two expressions, the difference is in focus.

• how about emphasizes the advancement of a new suggestion, while
• what about puts a little bit more emphasis on the request for information or feedback.

When you say "how about we get coffee?" you are primarily asking for an affirmative or negative reply. You are making a suggestion that you (normally) hope will be accepted. (This, incidentally, fits very closely with the fact that you can use a full independent clause with how about, since you need to be able to do that to make a suggestion or advance a complete idea.)

When you say "what about tea?" you are primarily asking for information or feedback on some thing (a noun or noun phrase, in this case—not an independent clause). In some cases it is an alternative given after a suggestion given with how about has been rejected, since (in that case) there is no need to mention the whole idea, but only one item in it.