Indirect questions are the one type of question that doesn't require a question mark. When you find yourself in class, looking out the window, daydreaming about your crush Bobby, you might be wondering whether or not he likes you back.
Your thoughts may sound like questions, but since you're not actually asking anything directly, they don't need question marks. The statement "I wonder if Bobby's heart flutters when I pass by" only needs a period at the end of it.
And some sappy flute music to go along with the sappy sentiment, probably.