A megapixel (mp) is roughly a million pixels ( 1,048,576 – 220 to be exact). The most common use of Megapixels is to refer to the ‘size’ of a sensor. A digital camera sensor may have 20mp. A higher number will mean that the sensor contains more pixels, but does not mean it’s a larger sensor – just denser, with more pixels per square inch.
A higher megapixel count does not always equate to a higher quality image as there are many factors that affect a sensor’s overall quality.