The 3D-array is a special type of
array that represents a three-dimensional ordered sequence of scalar (i.e. non-array) data.
See also the
array for an example of a 3D-array of integers.

In Excel, it is represented by N₁ ranges of cells with N₂ rows and N₃ columns.
The 3D-array can be thought as a
1D-array of which the elements are 2D-arrays
More precisely, a N₁ x N₂ x N₃ range represents a 3D-array that is regarded to contain N₁ elements, each of which is a 2D-array with N₂ rows and N₃ columns.
In other words, the convention of the data ordering in a 3D-array is first by the range counter, followed by rows inside the current range and then by columns in that same range.