What is the difference between DPI (dots per inch) and Pixels? Well, to put it simply, dots and pixels are the same thing. PPI would mean pixels per inch, exactly the same as dots per inch.
The files I give actors on a CD at the end of their session are 2848 X 4288 pixels each. DPI doesn't apply to digital files, as there is no such thing. It only matters when printing them, because it means basically how small the photo is. To find the number of inches the photos can print at 300 DPI, you divide the total pixels by 300. In this case, here is the math:
2848 pixels / 300 DPI = 9.493 inches
4288 pixels / 300 DPI = 14.293 inches
You can print a photo at 300 DPI of up to 9.5 X 14.3 inches with a 12.1 megapixel image.
If you wanted to only print at 72 DPI, lower quality, you could print at 39.5 X 59.5 inches, which is huge. 72 DPI would still look good (though not good enough for professional headshot prints).
Hopefully this clears things up. I often get questions from clients about this, so I figured writing this article could help explain.