Megapixels or MP is a value of one million pixels that is given to digital cameras to rate the capability and resolution of pictures the digital camera can take. In general, the higher this value is, the higher the resolution of pictures the camera will be able to take.
Note: With most cameras today the megapixels does not always mean higher quality. For example, you could have a 10-megapixel camera that takes better quality pictures than a 12-megapixel camera. The software and other technologies being used by the camera can also greatly affect the quality of a photo.