I have heard of the NIE number, what is this and will I need one?

An NIE number (sometimes also called a NIF number, but they are the same) is a fiscal number used to identify you on official papers. You will need one as you cannot legally buy a property, car or boat etc. without having applied and received your NIE documentation. You need to apply for your NIE/NIF personally and this can be done when you are in Spain.