A data dictionary is the start of a data catalog.  A data dictionary is information describing your data like content, structure, relationships, origin, format, etc.  This information is usually stored in tables, schemas, excel worksheets, and various other, sometimes random, places.  A data catalog is the next step. It gathers all of this information, builds on it with the help of stewards and AI-driven processes, and makes it searchable in one convenient place.  It creates an environment of collaboration to help your metadata grow and strengthen.