A "raster drawing" is a drawing given to the viewing application with 1 instruction: Draw exactly this. Image size and resolution were factored into the instructions when the image was made - in effect, it has already been drawn. Any attempt to change them must be done by the viewing application. With no further data available for resize beyond the original size, extrapolation delivers images of increasingly poorer quality.
Credits to Panda 'James Mark' Sherry
Raster chart data is created by scanning the information on a paper chart and storing this information in the form of pixels. Many thousands of pixels together make a flat digital image. Each pixel contains all the data for a particular point; colour, brightness etc. They are also geographically referenced which makes the raster chart identical in every way to the paper chart on which it is based. Raster charts cannot be manipulated or queried.
The example provides a zoomed chart extract. The decreased presentation quality can easily be seen.