What does DPI Mean??

this is something i struggle understanding- especially since my camera has settings to shoot for max resolution, and also need to know what settings i want depending on what size pic i want to print as- very confusing for me-

is there another thread on this somewhere?

There's DPI and PPI. When you talk about print quality, that's a product of PPI. Here is one of many pages that discuss the two.

As far as camera settings, always go with the best ("large/fine", or whatever it's called). Whether you want to put them to paper or on a website or anything else, you can resize later. It's [WAY] better to have a large original image that you can scale down than a small image and try to scale it up.

DPI = dots per inch
PPI = pixels per inch

Both are often used interchangeably, but DPI is really a measurement of how ink jet printers work, and it would be better to use PPI when discussing digital photo resolution.

PPI is scale. If I have a 300x300 pixel size image file and I display it at 100 PPI then it will be 3"x3". If I display it at 300 PPI it will be 1"x1". If I display it at 600 PPI it will be 1/2"x1/2". So by itself PPI tells us nothing about resolution. I can set a 10 x 10 pixel image to 300 PPI, but that doesn't change the fact that it's only a tiny reslution photo. Without the physical dimensions PPI is meaningless. If the minimum dimensions are not specified it's an indication the rule writer doesn't understand PPI. They just heard that 300 PPI is standard for high resolution. I get this all the time from magazines and websites that want to publish my photos. It does not inspire confidence that they do not understand the simple fundamentals of their job.

PPI can be changed at will with processing software. As long as the file is not resampled (changing the pixel dimensions) resolution does not change. If I have a 2000x3000 pixel photo it doesn't matter if it's 100 PPI, 300 PPI, or 600 PPI, the file remains the same. It's just a matter of how big it would print. You don't have to worry about PPI if you are not doing your own printing. The lab machines will set it to whatever is needed for the print size you order.

A bigger question for me is why do they need you to submit a high resolution file for a contest? If it's a print contest you should submit a print. If it's a web display contest then high res is not needed. I would examine the fine print very carefully before submitting anything. Many of these contests are tricks to collect free photos from amateur photographers rather than paying for stock photography or a pro. Never give up your rights to the photos. Real art contests will not ask you to do so. Possibly it's just a recommendation to help out amateurs, but be careful.