Short answers, pulled from the story.
An impression is a direct transfer from the original matrix and is considered an original work of art. A copy, by contrast, is a separate print that reproduces the first one. The term impression is the correct designation; copy refers to a distinct category.
Alois Senefelder invented lithography in 1798. The technique is based on the chemical repulsion between oil and water, using a porous limestone surface onto which the image is drawn with a greasy medium.
Etching is believed to have been invented by Daniel Hopfer, born around 1470 in Augsburg, Germany. Hopfer originally used the acid-biting technique to decorate armor before applying it to printmaking. The first dated etching is by Albrecht Durer, from 1515.
Since the late nineteenth century, artists have typically destroyed the matrix after printing a limited edition so that no additional impressions can be produced. This practice preserves the scarcity and integrity of the edition.
A giclée is a digital print made on an inkjet printer. The term was coined in 1991 by printmaker Jack Duganne. The word derives from the French word gicleur, meaning nozzle. Today it most often refers to pigment-based inkjet prints made on large-format machines.
Prints made on the best alkaline and acid-free paper have a life expectancy of over one thousand years. Average grades carry an expectancy of around five hundred years. Color prints are especially vulnerable to light damage and should be displayed at fifty lux or less.