It means that a person's skill and talent are best judged by the quality of their work. It emphasizes that true craftsmanship is evident in the final product, and not just in words or claims.
The phrase is often used in the context of:
* Evaluating artists, artisans, or professionals: Their work is the ultimate indicator of their abilities.
* Highlighting the importance of quality: The best way to demonstrate mastery is through creating excellent work.
* Emphasizing the connection between skill and results: The quality of the output reflects the quality of the creator's skill and knowledge.
This phrase is a reminder that true talent and expertise speak for themselves, through the tangible evidence of their work.