"what do you mean?","how do you mean?"how these two sentences are different?

1. What do u mean? ... Means that when some buddy does not get what other person is saying then first person asks to whom he or she is listening “what do you mean”.

2. When a person does not get what’s the reason of second person’s meaning of saying then first person might ask how do you mean? ….. To figure out the reason of a speaker’s meaning

"what do you mean?","how do you mean?"how these two sentences are different?

Very Simple .I say the glass has half water & you say the glass is half empty.

All the words means depends on you & the situation it changes.

What mns the point whereas how mns the way which is it to b adopted....