Carto is using Mapbox technology in the background. This blog posts explains some differentiation on top https://carto.com/blog/partnering-with-mapbox/

Carto uses geocoding and routing services from Mapbox - but their vector and raster map tiles are powered by OpenMapTiles. See: https://blog.klokantech.com/2018/05/openmaptiles-gives-you-f...

Carto offers many of the same services, but their focus is more on the ability to analyze vs display data. Their big sales push is "Location Intelligence" vs simply providing various standard geoservices.

I consider Carto and Mapbox to be tangential services in many respects.