There are many ways to print photos. For example you could download the photos to your computer choose the ones you like burn them on a CD and take them to a printing service. DPOF makes such photo printing easier - here is how.
DPOF is a standard that was introduced by a consortium of camera and printer manufacturers. The goal of DPOF was the make photo printing easier and faster.
DPOF stands for Digital Print Order Format. The goal behind DPOF was to make the process of choosing which photos to print and printing them much easier and faster. If your camera supports DPOF then you can choose the photos you would like to print and the number of copies directly on your digital camera. This data is also known as the print order and is saved in the cameras memory card (the same memory card where photos are saved) in special files. Later on you can take the memory card with the photos and the DPOF data to any printing service that supports DPOF and it would automatically print the photos based on the DPOF print order data. Alternatively you could plug the memory card to a photo printer that supports DPOF and print all the photos that you chose with a single push of a button.
DPOF can do much more than just specify which photos to print and in how many copies. You can also specify additional information such as a photo title text, photo orientation, print paper size and more. Other useful information can be added: your contact information and your camera settings when taking the photo. All that information can make printing easier - for example you can drop off a memory card with any printing service and they can know exactly which photos to print, in how many copies on what paper sizes and in what orientation. They also have your contact information where they can reach you when the prints are ready or if there is any problem.