Analog resolutions are usually referred to in TVL (TV Lines).  420 TVL, 480 TVL, 540 TVL, 600 TVL, 700 TVL, 1000 TVL - What are TV-Lines really?  It is easier to see the difference between analog and mega-pixel using a picture showing the same scene at different resolutions.

The QVGA image is 1,228,800 megapixels just less than the 1.3mp or 720P.  By comparison a 700TVL camera has about 480,000 pixels.  

The 1.3mp is 3X the quality of a 700TVL camera and the 2mp is about 5X the resolution.

Our HD-CVI and IP systems are both now 1.3 or 2mp and the IP system will have 4mp cameras available very soon.

These resolutions give a wider viewing area and allow greater distortion free digital zoom.