CartoCSS is one the tools of the CARTO platform. You can learn more about the different [components of CARTO platform]({{site.fundamental_docs}}/components/), or directly dig into [CartoCSS too]({{site.styling_cartocss}}/) details.
Spatial resolution in pixels. A resolution of 1 means no spatial aggregation of the data. Any other resolution of N results in spatial aggregation into cells of NxN pixels. The value N must be power of 2.