It is an equivalent to English "in order to" and "for the purpose of", Jonathan.

The infinitive in English has a lot of functions. One of them is to express purpose. For example: The man came up to the door to close it. "To close" is the infinitive of purpose. In Russian we use the infinitive of purpose too but must use the word "чтобы" before it. For example: Мужчина подошел к двери, чтобы закрыть ее.

We use it like: for something. It is an aswer to "What for?" For example - Зачем? Чтобы быть счастливым. (What for? For being happy.) This word stays before the explanation of what for do you need/do/ask (or something else) anything.

Thanks everyone! That's really helped :D

Mate, it's the same thing as the infinitive of purpose. I am saving money to buy a car. - Я коплю деньги, чтобы купить машину. I have called you to talk. - Я позвал тебя, чтобы поговорить.