Bitmapping vs. vector graphics
Unlike a vector graphic, which is rendered according to mathematical formulae which can scale to any size, a bitmapped graphic loses quality when scaled. When scaled up, the pixels of a bitmapped graphic must be interpolated, which can produce a blurry image. When scaled down, the pixels of a bitmapped graphic must be resampled, which results in the loss of image data.
In general, vector graphics are best suited for artwork composed of geometric shapes, such as a logo or a digital drawings, and bitmapped graphics are best suited for photographic images.