Two-dimensional spaces, also known as planar spaces, are areas that exist in two dimensions. They are typically represented by a flat surface, such as a graph or a map, and can be measured in terms of length and width. Two-dimensional spaces are often used to represent physical objects, such as buildings or landscapes, and can also be used to represent abstract concepts, such as mathematical equations. The term 'AREAS' is an appropriate solution for this crossword puzzle, as it accurately describes two-dimensional spaces.