Vector art is made up of scalable parts defined by mathematical equations rather than pixels. The parts are editable and maintain the highest quality in all scales and media, including on screen and in print.
The biggest advantage to using vector images versus bitmap images is the scalability. Vector images can be resized in dimension or resolution without any loss of quality. Text is vector-based, which is why it can be scaled and always remain perfectly crisp. Vector images can also be any shape, which means there are no blank white rectangular backgrounds around them as there are with bitmap images. Because vector images cannot display the wide array of gradients seen in bitmaps, they often have a cartoonish look and are rarely used for photorealistic graphics.