Etching is a printmaking technique where an artist scratches a design through an acid-resistant ground on a metal plate which is then dipped in acid to etch the design. The plate is then inked and printed, with the etched lines holding the ink. The document discusses the history of etching from the 15th century, profiles famous artists like Rembrandt and Picasso and their etching works, and describes different etching techniques like soft ground etching.