Very simple: A proof is the simulation of a later print, either as soft proof on the monitor or as contract proof, validation print or as form proof on paper.
Softproof: A softproof is the color-accurate representation of the print on a monitor. This can be done either at the agency or directly at the printing machine, for example, so that the printer can coordinate the production run with the soft proof.
Contract Proof: The “highest” level of proofing: A contract proof is a very high-quality simulation of the subsequent printing result, and is nowadays actually always produced with special inkjet printers on special paper with special software. The UGRA/Fogra media wedge print makes the proof “colour and legally binding”. In the best case, the media wedge is checked directly during proof production with a measuring device and a test report is glued or printed on which confirms compliance with the tolerances.
Validation Print: A Validation Print has higher tolerances regarding the color deviations from the given standard than a contract proof. It is therefore not “colour and legally binding”, i.e. it does not serve as a contract or “contract” between the designer and the printer, unless both parties have agreed that Validation Print can serve as a colour reference. Validation prints are often used in the coordination process in agencies or as quick templates with good colour matching, as they can also be produced on current laser and LED or other digital printers. Compared to inkjet printing, these printing systems are many times faster and cheaper.
Form Proof: A form proof is often found in print shops; large sheets of paper on which the finished imposed sheets, e.g. of a magazine, are printed. Form proofs are printed with inexpensive inkjet plotters on inexpensive paper and usually look terribly coarse and pixelated, even the colors are terrible. However, the data for the form proof runs through the same workflow with which the printing plates are later produced. This means that what can be seen on the form proof can later also be seen on the printing plate. Thus, the final printing forms can be optimally checked once again to ensure that all fonts, images and embedded graphics are displayed correctly. However, a form proof is by no means binding in terms of colour.