In digital imaging, a pixel is a physical point in a image and each digital image is made up of a series pixels. The megapixel value is simply a shorthand means of expressing the camera's image resolution in a single figure.
1 Megapixel = 1 Million Pixels
Multiply the horizontal resolution by the vertical resolution to arrive at a value which expresses the total number of pixels that the image device can deliver. Higher resolution gives you the ability to enlarge an image and see critical details at a greater distance than before.
The image below depicts the video image difference between various video streaming technologies. Analog systems typically provide top resolution of 960x480 pixels, significantly smaller than the image provided by HD Plus megapixel cameras. 1080p high definition is 1920x1080 pixels, similar to a 1080p HD television. A high-end 4MP IP camera can capture video at 2560x1440 pixels. That’s more than 75% more pixels than 1080p!
"It's like putting on glasses"
As you can also see from the image below. HD quality digital video give you the clarity that can never be matched with an analog CCTV video system.