It is useful to understand the difference between bitmap and vector graphics for use in producing documents for presentation of scientific data. Images acquired by scanning or digital photography are bitmap or raster images. A bitmap image is made up of pixels, each is individually stored with a specific location and color value. Bitmap images are resolution dependent, and they can appear jagged or lose detail when scaled to higher resolutions. This is especially apparent with bitmapped text.
Vector images consist of lines and curves defined by mathematical objects called vectors.
The color and position of vector objects are stored within the definition of the object. Vectors are not resolution dependent and can be scaled without loss of quality. There are a large number of graphic file formats in common use. Fortunately, you only need to use a few of these in day to day practice. Knowing which formats to use for which purpose is the important issue.