Bitmap graphic formats treat each graphic as a collection of dots, assigning a specific color to each pixel. When viewed as a whole, the collection of pixels forms an image. While this approach can work well when the image is viewed at its intended size and resolution, bitmaps will often appear jagged and blocky when viewed close up.
Vector graphics define images through shapes and paths.
This means that a circle created as a vector graphic remains as smooth as the device you are viewing the graphic on will allow, regardless of how much is it enlarged by zooming or resizing. While bitmaps are well suited for electronic representation of photographs and static images that will not be modified frequently, the demands on Web graphics are evolving beyond the limitations of the bitmap file format. Vector graphics, however, can display high levels of detail at multiple zoom levels. As a simple but powerful example of where the scalability of vector graphics would be advantageous, imagine a medical diagram. Both vector and bitmap formats could display the diagram at its normal size.