Native Spanish speakers and those who have ever taken Spanish will immediately recognise the inverted question mark - ¿ - in the Spanish language, questions are not just ended with a question mark as in English, but are surrounded with them. For example: ¿Cuántos años tienes? means "how old are you?".
This practice is actually quite useful. By using the question marks like inverted commas or parentheses, questions are clearly marked. But why don't we do this in English?
The answer is very simple: word order.
In English, we have our own way of disambiguating between statement and question sentences - we change the order of the words, or add in auxiliary question words. For example: "You are going to the store." / "Are you going to the store?". We also mark it with a question mark, and, when spoken, raise the intonation of our voice in the last word (although this is becoming fairly common in statement sentences for certain American accents).
In Spanish, the word order remains the same, and the only clue that the sentence is a question are the question marks. So, to use the same examples as above: "Vas a la tienda." / "¿Vas a la tienda?".
However, since the preceding question mark is really just a flag that a question is coming, unless the question is very long, Spanish is slowly moving towards ditching the ¿ entirely in informal situations. In internet chat rooms, for example, the ¿ is often omitted since it's faster and easier for people just to type the final question mark.