Images can be saved in an interlaced format, so that rather than consecutively displaying the lines that make up the image, the image displays every eighth line and than every fourth line so that the viewer can see a preview. Presenting interlaced images lets the reader begin scrolling through the page while the image loads. Interlaced GIF's, Progressive JPEG's, and PNG's are all examples of interlaced file formats.
The process by which a monitor draws only the even or odd horizontal lines With each vertical refresh. This allows the monitor to draw twice as many Lines per refresh. However, if you are using an application that requires Fast refreshes, like streaming video or animations, this can create flickering and a chunky feel.
A system developed for television which divides each video frame into two fields (upper and lower). This is done by first drawing one field consisting of an image’s odd scan lines (1, 3, 5... 525) and then drawing the remaining even scan lines (2, 4, 6...), interweaving both fields. Interlacing reduces the perception of screen flicker. Interlacing can cause annoying effects with images such as computer generated text and graphics when transferred to video.