Resolution is often described in terms of megapixels. Most digital cameras have 4 or more megapixels—which take pictures that are roughly 2,200 pixels by 1,700 pixels. (To find out your camera's megapixels, multiply the height and width and round to the nearest million.) The more megapixels you have, the more details and sharpness your pictures will have.
You will run into trouble with resolution if you begin manipulating the image with computer software—especially if you want to crop in close on one element in the photo. The basic mantra is: the bigger the better. To ensure you will be happy with the results, make sure you camera is on the highest resolution settings possible and be conservative with cropping.
About the photo: This November 2003 close-up photo by Jodi Cobb is of a Huli wigman in Garoka, Papua New Guinea.