An original print is an image that has been conceived and executed by the artist soley as a print, usually in a numbered edition, and signed by the artist. Each print in the edition is an original that has been hand printed from a plate, stone, screen, block or other matrix created for that purpose.
A reproduction (although often called a print) has no relationship whatsoever to an original print. it is a copy of a work of art conceived by the artist in another medium (painting, watercolour, etc.). The reproduction has usually been made by photo-mechanical means. Numbering and signing a reproduction does not change its essence; it is still a reproduction of a painting, watercolour etc. It is not an original print.
Watch an interactive, animated demonstration of the four main printmaking processes – relief, etching, lithography, and screenprinting – on the Museum of Modern Art (MOMA) website. It also includes images of more than forty prints from the MOMA collection in order to demonstrate the range of effects that are associated with each technique.