To understand pixels, one must first remember the good old days when you took pictures on film and let the development labs worry about pixels. But, they didn't really have to, because the exposed negative just captured the image that was reflected through the lens. It was all there and the only thing that affected quality was the size of the negative. The bigger the negative was, the larger the picture that could be produced. When the world went digital, the pixel was invented. So what is a pixel? If you divided a picture in hundreds of horizontal and vertical lines, you would actually have a large number of little squares that when put together, created the picture. Each square is a pixel. So, when a digital camera says it has 1-megapixel capabilities, it means that the total number of horizontal and vertical squares produced when a picture is taken equals 1 megapixel (1,000,000 pixels).
A 3 megapixel camera produces a picture that has 3 million pixels in its makeup. If all the pictures were the same size in each camera, it would be easy to understand why a camera that produces more pixels would be a better quality camera. Here is where the camera makers are not forthcoming with information. What they don't tell you is that as far as I can tell, every digital camera produces pictures that have 72 pixels per inch per picture both horizontal and vertical. The only difference is that a 3 megapixel camera produces a larger picture than a 1 megapixel camera and a 5 megapixel camera produces an even larger picture yet. The reason I say "as far as I can tell" is that I have not tried all cameras or studied the information on all cameras. There may be some out there different, but they probably are not in the amateur photographer's price range.
Conclusion:
For video uses only, your camera purchase decision should be based on features other than the number of pixels.
