There are three different ways to end a sentence. There is a correct use for each, despite the fact that they are frequently confused.
The full stop is used at the end of a sentence that is not a question or an exclamation.
The question mark is used at the end of a question. This may seem obvious, but it can be misused. Make sure that the sentence is a question, and always do use a question mark when asking a question – even if it’s a heading or a title.