"How are you?" is a nice question. It's a friendly way that people in the United States greet each other. But "How are you?" is also a very unusual question. It's a question that often doesn't have an answer. The person who asks "How are you?" hopes to hear the answer "Fine.", even if the person's friend isn't fine. The reason is that" How are you? "isn't really a question and "Fine." isn't really an answer. They are simply other ways of saying "Hello" or "Hi".
Sometimes, people also don't say exactly what they mean. For example, when someone asks "Do you agree?", the other person might be thinking, "No, I disagree. I think you're wrong." But it isn't very polite to disagree so strongly, so the other person might say "I'm not so sure. "It's a nicer way to say that you don't agree with someone.
People also don't say exactly what they are thinking when they finish talking with other people. For example, many talks over the phone finish when one person says "I have to go now." Often, the person who wants to hang up gives an excuse, "Someone's at the door." "Something is burning on the stove." The excuse might be real, or it might not. Perhaps the person who wants to hang up simply doesn't want to talk any more, but it isn't polite to say that. The excuse is more polite, and it doesn't hurt the other person.
Whether they are greeting each other, talking about an idea, or finishing a talk, people often don't say exactly that they are thinking. It's an important way that people try to be nice to each other, and it's a part of the game of language.
