Well there are two types of space in design, positive and negative space. Positive space contains all of the elements of your site, i.e. content, navigation, images, etc. Negative space (often referred to as whitespace) is all of the empty space in between, i.e. the space around the content that separates the elements and helps to structure and define the way the user interacts with the content in the positive space.
Having said that, there are also two types of negative space: micro and macro.
