Nancy, to answer a few ??
RAR - there is another zipping program out there called winRAR, it uses the extension .rar , if you don't own this program, you cannot unzip .rar files. ZIP files are universal and everyone can access, hence the reason we want ZIP
Adobe Illustrator is an example of a Vector Program, I can't really explain what a vector is, I know how to use them and what programs to use with them, but I'm unsure of the exact definition, so maybe someone can explain that a little better
72dpi - this is the image resolution. 72 dots per inch is the standard web resolution for images, where as 300 dots per inch is the standard for print quality images. Most digital kits are designed at 300dpi for optimal printing, however, previews have to be resized down to 72dpi for posting on the web, ie our gallery...