First, some background information about how a television set works. The CRT (cathode ray tube) TVs that some of us grew up with displayed a picture due to a gun shooting a stream of electrons across the screen in lines from left to right, starting at the top of the screen and moving down to the bottom. The phosphors coating the screen would glow as they were hit by the stream of electrons. Since the early TV sets weren't able to display the entire picture on the screen without the top fading by the time the bottom was visible, manufacturers came up with a system in which only half of the lines of the display were refreshed each cycle, while the alternate lines were refreshed the next cycle. This is called interlacing, and it sometimes results in distortion if the images are those of a quickly moving subject. TV images are usually generated at 50 cycles per second.
TV technology has significantly advanced, and progressive scanning was developed. This is what the "p" in 1080p stands for, as opposed to 1080i, where the "i" stands for interlacing. A TV that's 1080p doesn't display a picture using odd and even lines, but rather the entire image is seen at once, similar to movie films. The 1080 refers to the resolution of the TV set. While the old CRT television sets used to display 576 horizon lines, the new digital high-definition (HD or high-def) TV sets boast 720 or 1080 lines that make up the image displayed, which gives a higher resolution. Indeed, you may find that digital pictures are four times sharper and clearer than analog ones.
Currently, 1080p HD TV gives you the best picture available. Its resolution is 1,920 x 1,080 pixels, and all the lines of the image are visible at the same time. Since it's smoother than 1080i, it does a better job, especially when capturing sports events and other action footage.