This correction is better understood with a few pictures and with an analogy. We can think of volume (i.e. 3D) anamorphic distortion as the photographic equivalent of the problem that mapmakers have when trying to represent our 3D planet on a two dimensional sheet of paper. Mapmakers know that it is impossible to conserve all the properties of the earth's features (surface, distances, etc.) on a flat surface. Mapmakers choose the best trade-off for the objective they are trying to achieve.
The same applies to photography - 3D objects (people, faces, or columns, for example) can appear distorted when projected on the camera's sensor. People's appearance at the edge of a group, architectural shots or crowd close-ups can be vastly improved with just one click of DxO Optics Pro's feature.
Simply choose the type of shape being distored (e.g. cylindrical, such as people in a group shot, or spherical, such as for heads in a news shot) and let DxO Optics Pro do the rest. The results are remarkable!