A megapixel is one million pixels. It is commonly used to describe the resolution of digital cameras. For example, a 7.2 megapixel camera is capable of capturing roughly 7,200,000 pixels. The higher the megapixel number, the more detail the camera can capture. Therefore, the megapixel count is a significant specification to look for when buying a digital camera.
A camera's megapixel number is calculated by multiplying the number of vertical pixels by the number of horizontal pixels captured by the camera's sensor, or CCD. For example, the original Canon Digital Rebel captures 2048 vertical by 3072 horizontal pixels, for a total of 6,291,456 pixels (2048 x 3072). Therefore, it is estimated to be a 6.3 megapixel camera. The Sony T10 captures 3072 x 2304 pixels, totaling 7,077,888, which makes it a 7.2 megapixel camera (because not all the pixels are used).
Megapixels are helpful in marketing digital cameras, because it is easier to say, "6.3 megapixels" than "6,291,456 pixels." It is also a little easier to remember. However, while megapixels are important, it is helpful to know the other specifications of a camera as well. For example, shutter speed, shooting modes, start-up time, flash quality, and color accuracy can also make a big difference in the camera's performance. After all, it doesn't matter how many megapixels your camera has if all your pictures turn out blurry and have poor color. Therefore, while you should check the megapixel count on a camera before buying it, make sure you check the other specs too.