When you're talking to a Web designer, they might mention GIFs or JPEGs. These are file formats for graphics. GIF stands for graphics interchange format, and JPEG stands for joint photographic experts group. You might see JPG instead of JPEG, which is most commonly used on PCs vs. Macs.
Both file formats use compression mechanisms to reduce a digital image. JPEGs work best for photographs while a GIF works better with line drawings or illustrations. Graphics saved as JPEGs are said to download faster than GIFs, but they can't be made transparent or interlaced.
Transparent GIFs allow the background of a graphic to be made transparent, which is handy to achieve certain designs. Interlaced GIFs appear to "fade in" as opposed to appearing like a Venetian blind from top to bottom. The image starts off blurry and comes into focus, giving a feeling of downloading more quickly because you see the full image immediately, even if not clearly.
Aliza Sherman is an entrepreneur and author of Cybergrrl: A Woman's Guide to the World Wide Web (Ballantine Books). She is currently working on her next book and new company.