I apply a coating to a polished copper plate; with a rounded needle, I draw through the coating.
Immersion in ferric chloride etches the areas of exposed metal.*
I may also use a drypoint technique, scratching into the copper.
Ink is applied, and wiped off, but it remains in the etched grooves.
In the press, fine paper is forced against the plate; ink is transferred to the paper.
Not a cheap photo-mechanical reproduction (like the pretentiously-termed gicleé made with an ink-jet printer), an etching is an original print because each one is inked, wiped, and printed by hand. It has a distinctively tactile ink surface and plate impression, and no two are exactly alike.
* FeCl3+Cu+H2O=FeO+CuCl3+H2