Megapixels

A camera's CCD consists of millions of pixels, each one building up a tiny charge of electricity in response to the light it "sees." The more pixels a CCD has, the higher its resolution.

The effective pixel count is the the number of pixels that are actually used when a picture is taken, because some pixels on a CCD don't get used for picture information. Effective pixel count is a more accurate way to assess a camera's capacity.