1080p represents 1,080 lines of resolution scanned sequentially. In other words, all lines are scanned in progressively, providing the most detailed high definition video image that is currently available to consumers.
Access to 1080p is determined by whether your HDTV has the ability to access a 1080p signal from a source directly, or your HDTV has to scale and process all signal inputs to 1080p internally.
1080p/60 vs 1080p/24
Almost all HDTVs that accept a 1080p input signal directly accept what is known as 1080p/60. 1080p/60 represents a 1080p signal transferred and displayed at a rate of 60 frames-per-second (30 frames displayed twice per second). This is a standard progressive scan 1920x1080 pixel video signal.
However, with the advent of Blu-ray Disc and HD-DVD, a variation of 1080p is being promoted and implemented: 1080p/24. What 1080p/24 represents is the frame rate of standard 35mm film transferred directly in its native 24 frames-per-second from a source (such as a film on a Blu-ray or HD-DVD disc). This means that in order to display this image on an HDTV, the HDTV has to have the ability to display 1080p resolution at 24 frames per second.
Up to this point, most Blu-ray Disc and HD-DVD players read the 1080p/24 format information off of the disc and then reprocesses it so that it will be able to output the signal as 1080p/60, thus making it compatible with most 1080p input compatible HDTVs.
However, most Blu-ray Disc players can also output 1080p/24 off the disc directly and send that signal unchanged to an HDTV. In this case, if the HDTV cannot process or display the 1080p/24 signal directly, the Blu-ray Disc player will then reprocess the 1080p/24 signal to 1080p/60 so that the HDTV will recognize the signal.
DVD Resolution Upscaling
Although standard DVD is not a high resolution format, most DVD players now have the ability to output a video signal in the 720p, 1080i, or 1080p format allows the DVD player's video output to more closely match the capabilities of today's HDTVs.
Although upscaling standard DVDs is not the same as watching DVDs in true-high definition, as current DVDs are not recorded in high definition, you will experience increased detail and color you didn't think was possible from a DVD player. Blu-ray Discs and HD-DVDs are the only true source of full 1080p high-definition video in a disc-based format.
Video upscaling works best on fixed pixel displays, such as LCD or Plasma sets, the upscaling may result in harsh images on standard CRT and CRT-based Projection sets. In addition, if your television has a native display resolution other than 720p, 1080i, or 1080p, the TVs video processor will rescale the incoming signal to its own specification, which can also yield different results on the final, displayed television image.
Don't Get Confused
If you are still a little confused, you are not alone. Remember, video resolution can be stated either in lines or pixels. However, don't get caught up in all the video resolution numbers. Look at it this way, VHS looks great on a 13-inch TV, but "crappy" on a big screen.
In addition, resolution isn't the only factor that contributes to a good TV image. Factors such as color accuracy, contrast ratio, brightness, maximum viewing angle, and whether the image is interlaced or progressive, all contribute to quality of the picture.
You can have a very detailed image, but if the other factors mentioned aren't sufficiently present, you have a lousy TV. Even the best TVs can't make a poor import source look good. In fact, ordinary broadcast TV (with its low resolution) sometimes looks worse on an HDTV that it does on a good, standard, analog set.
For an additional look at high definition resolution that may help in your next TV purchase, check out the article from About.com's site for TV/Video: Which HDTV Should You Buy: 720p, 1080i, 1080p?.
In conclusion, this article was intended to provide an overview of the basic principles regarding video resolution. This was not intended to be a technical dissertation and more detailed, related points were not elaborated. However, for those that wish to dig deeper into high definition video resolution, check out the following articles: