What 什么 How 怎么 That is the mean difference when they are used on their own. Expressions like 'what about ' and 'how about' do have almost he same usage, you can interchange them in most contexts.

These terms are used to ask questions Examples: What is your name? How do you spell your name? What is the weather like today? How soon will it rain? What about/ how about going to the movies?

'What' is the question we ask when we want to know the nature, class, name or purpose of something.'What is your address?' 'How' is the question word we use when we want to know about manner or way 'How do you cook an egg?'/ state or condition 'How are you?',/ extent, degree or amount. 'How much is that doggie in the window.' 'What about' and 'how about' are used in the same way either to a)make a suggestion. 'How about/what about going to the cinema tonight?' or b) to ask someone the same question as they have asked you. 'How are you?' 'Very well, thank you, What about/ how about you?

what可以做主语，一般用于疑问句时，所要提问的对象一般是sth. eg:What is it? What i want to say is that…… how作主语表方式，状态之类的。eg:How are you? How did you do that? what about一般后面接doing “how about” 跟what about 的具体的difference我也不知道，反正在考试里how对方式提问 what对事情，东西提问