Pixels can relate to a large number of contexts, included printed pixels on a page, pixels on a display device, pixels in a digital camera photosensor or even pixels carried by electronic signals. The most notable is using pixels as a measure of Resolution, notably on TVs and monitors.
The more pixels used to represent an image, the sharper and clearer the result will resemble the original image. Pixels are often confused with resolution and although they are very similar there are distinct differences. Pixels can be counted as a value, such as a 3MP camera will have three million pixels, where as resolution needs an X and Y axis value, such as a monitor with 1280 pixels by 800 pixels resolution.
Relevant Guides
Resizing DVD-Video To Square Pixels- When deciding on settings for encoding MPEG-4 video with any tool, one of the most misunderstood subjects is resizing. For many people the easy solution is to rely on their video encoder to select the best settings, but you can't necessarily count on the software's decision making. While more advanced open source tools tend to do well on resizing decisions, common (and generally high quality) commercial tools used by many consumers don't seem to do as well. Although it's a bit more work to figure out the best settings for your own encodes, once you do the work once you should have a system you can apply to all your encodes to obtain maximum quality.
