All digital graphics can be broken down into two separate camps: raster images (also referred to as bitmaps), and vector artwork. Rasters are made up of a finite number of pixels, and image quality degrades as it is scaled up in size. Vectors are defined by mathematical equations and remain "crisp" no matter how large they become. Even more complex data such as relative line weights and color gradients can be stored algorithmically. One way to distinguish between the two is to simply open up the file and zoom in on the linework. If lines remain sharp and hold their form, it is a vector file; if, on the other hand, they degrade and show pixelation, you have a raster file. These two formats even encompass 3D designs, as the same principles are simply expanded into the z-axis.
The primary benefit of vector artwork over raster is quite simple: you can easily create a raster from vectors by "printing," "publishing," or "rendering it at virtually any given dimensions. However, the reverse is not true. While there is some software available that is able to automatically vectorize (digitize) a bitmap, the results are often not very accurate. Detailed and intricate designs must be done manually by a skilled artist who will trace over and redraw the original in a vector format.
Common file formats of raster images include:
.JPG .GIF .PNG .BMP .TIFF .PSP
Common file formats of vector images include:.AI .DXF .SVG
(Note that vector files may also contain or reference bitmap images within them.)
Common mixed formats that often contain both types include:
.PSD .PDF .EPS .SWF