What was a "Renaissance man" how did the Renaissance artists fit into this?

Leanardo da vinci and michelangelo they both painted and contributed to the renaissance

the renaissance was the rebirth of greek and roman designs

How did the Renaissance artists fit into this? He was most famous as a painter, but he was also a scientist, engineer and mathematician. Leonardo is called a "Renaissance man". Another "Renaissance man" was Michelangelo, who was a sculptor, painter, architect and poet.