A good share of our communicating with one another is made up of asking questions. What time is it? Is that the house over there? Did you call the owner? You have some information I would like to have, and I can request it from you by changing the way I organize my sentences. But because we inevitably involve ourselves with others when we ask a question—and because human relations can be so subtle at times—we can ask for information in more than one way: directly, indirectly, and even merely seemingly.
If I don’t know what time it is and I presume you do, then I can pose what is called a direct question: What time is it? You will first suspect I am asking a question because you will hear or read the statement beginning with an interrogative pronoun (what), and that suspicion will be confirmed when you soon see the verb coming before the subject (is it) and the sentence ending with a question mark. This way of designing a question, when at least some part of a predicate precedes the subject, involves what is called the inverted order; it is said to be inverted because it reverses the standard English word order of a subject followed by a predicate. The predicate of a sentence, of course, means that section that includes the verb and any other words which the verb might need to complete its picture.
Another way to directly pose a question is to employ the verb do as an auxiliary and combine it with an infinitive: Do you know what time it is? Did you call the owner? In this alternate interrogative construction, we retain the inverted word order (do you, not you do), expressing the tense in the auxiliary verb (as is always the case in a verb phrase) in order to chime a note of emphasis: Do you know what time it is? asks for the same information as What time is it? but with a bit more urgency because of its more elaborate form. The auxiliary do + infinitive construction is the same one we use to build the emphatic aspect of an affirmative statement (I do know what time it is), the only difference being that we invert the order of subject and predicate for a question.
But what happens if I wish to relate to you a question someone else posed. If I say, for example, he asked what time it was, I am not directly asking you what time it is. I am instead telling you that someone asked that question. This construction is called an indirect question, and it is formed by using some verb of asking or knowing in the main clause, and then putting the question (in its regular, not inverted, form) in a subordinate clause. Thus, in the indirect question he wondered what time it was, the verb wondered connotes the idea of asking, and what time it was comprises a subordinate clause in its standard word order. Indirect questions are used to report a question (whether in the past, present, or probable future) and they are closed with a period, not a question mark.
Finally, what about an exchange like this: It is important we make a decision about this soon. Would you email me the report by tomorrow, please. Is the second sentence really a question? Listen closely and you can hear a request or even a subtly veiled command, because in the context, the speaker is almost certainly not asking someone to answer yes or no. Such seeming questions are called courtesy questions. We can think of them as polite imperatives, and as commands, though gentle, they do not close with a question mark, but with a period.
Direct questions, indirect questions, and courtesy questions—three ways to garner information differently. Their uses remind us of the subtleties of our relationships and how those complexities can be represented in the language we write and speak.