It provides a grid of n-dimensions where n represents how many keys can be used to reference a single point.
A grid file can be used to provide an efficient index for this structure, where records come in groupings of 26, each of them relating to street names in a city starting with one of the letters of the alphabet.
This structure can be thought of as an array, table, or grid with two dimensions which we will call the x and y axes.
This would cause records in the same bucket to correspond to households on a street beginning with the same letter, in the same city, in the same continent.
The cells in the grid file would then consist of a city header, and six (one for each continent, not including Antarctica) groupings of 26 cells relating to the streets with the same starting letter, in the same city, on the same continent and could now be thought of as a three-dimensional array.