There are 2 main types of questions. Open and closed questions. Closed questions are those for which the answer can be only 'yes' or 'no'. These questions are usually formed by putting the auxiliary or modal verb in front of the subject. Do you like pizza? (present simple) Is he going to Paris? (present continuous) Will they be at the party?( future with will) Did you like the film? (past simple) Can you swim?etc.
Open questions ask for more information and are started with a interrogative word or phrase such as What, How, Who, When, Which (film). This word or phrase goes in front of the auxiliary or modal verb. When are you going to Paris? How can I help you? Which film (interrogative phrase) did you see?
The only exception to this rule is the verb 'to be' which does not take an auxiliary in the present and past simple tenses. here we just invert the subject and verb in open and closed questions.
Are you tired? Were you late for your appointment? How are you?
However, we don't add an auxiliary for subject questions.
In questions where the question word or phrase is the subject there is no added auxiliary in the present or past simple nor any inversion. Who plays football in this class? Which car will arrive first? Who loves you?