Screen resolution on your monitor is 72 ppi and images looks good on your screen at that resolution. This means there are 72 tiny dots on the vertical and horizontal axis, which are used to make the image look real. Magazine printing is often 250 ppi or higher. Multiplying the vertical and horizontal axis will give you a much larger number of pixels than screen resolution. This is why graphics, which look good on screen, look jaggy on the printer.
Printers require higher resolution to look decent.
A final copy of the artwork for your print piece supplied for your approval. It is your responsibility to go over it with a fine toothcomb to insure that it is exactly what you wanted, clearly noting changes as necessary, which will necessitate another proof. Your signature will approve it for printing. Printing cannot proceed with your approval of the proof. Short Run Short run refers to print orders of less than 500 copies.