Definition of 'Proof'
An impression of a print made before an edition to check the quality of the work. Proofs became more common with the advent of widespread printing, and may contain only the image and none of the accompanying text that the final impressions contain, as it is considered a rough draft.
Investopedia explains 'Proof'
There are several types of proofs available to collectors, including artist’s proofs, B.A.T proofs, and printer’s proofs.
A trial proof is a proof created before a production run, and is created to ensure that the proof being created properly. There may several trial proofs, and the number depends on whether the artist makes adjustments to the material.
A bon à tirer (B.A.T) proof is the final trial proof of the artist before the printer begins a production run. This type of proof was used to tell the printer, who may not be the artist, how the proof should look. There is generally only one B.A.T proof for each edition.
An artist’s proof is an edition provided to the artist by the publisher. The artist is allowed to sell his or her portion of the edition.
A printer’s proof is a copy provided to the printer for free by the print publisher. There can be more than one printer’s proof for each edition.