Modern printing methods such as laser and ink-jet printing are known as digital printing. In digital printing, an image is sent directly to the printer using digital files such as PDFs and those from graphics software such as Illustrator and InDesign. This eliminates the need for a printing plate, which is used in offset printing, which can save money and time.
Without the need to create a plate, digital printing has brought about fast turnaround times and printing on demand. Instead of having to print large, pre-determined runs, requests can be made for as little as one print. While offset printing still often results in slightly better quality prints, digital methods are being worked on at a fast rate to improve quality and lower costs.
See The Digital Printing Process Below:
http://www.youtube.com/watch?v=BRYpSkBfTug