Vector graphics is the use of geometrical primitives such as points, lines, curves, and shapes orpolygon(s), which are all based on mathematical equations, to represent images in computer graphics.
Example showing effect of vector graphics versus raster graphics. The original vector-based illustration is at the left. The upper-right image illustrates magnification of 7x as a vector image. The lower-right image illustrates the same magnification as a bitmap image. Raster images are based on pixels and thus scale with loss of clarity, while vector-based images can be scaled indefinitely without degrading quality.
Source: Wikipedia
