The auxiliary verb 'to do' is used in questions and negative forms of simple tenses - for example, 'I live', 'He speaks' (present simple) and 'I lived', 'He spoke (past simple). It's followed by the base form of the verb e.g. speak (not speaks or spoke) . Here are some examples: Where do you live? What did you do last night? The verb 'to be' - am, is, are (present) , was, were (past) - is part of the form of continuous (also known as progressive) tenses. It goes with the present participle of the verb, the --ing form. To make a question in a continuous tense, you put the verb 'to be' before the subject. For example: Where are you going? What was John doing last week? I hope that helps.