A plotter is a large scale printer for printing graphics and are employed by graphic designers, engineers and architects and is primarily used by companies that produce large amounts of detailed line drawings. Plotters use a custom-designed pen (or set of interchangable pens/drawing attachments) attached to an arm that can move side to side, and to a drum that can rotate smoothly through 360 degrees, to draw line art onto a page. This is something that would be incredibly expensive (or even impossible!) to achieve with even a top quality inkjet, and can be done so much more inexpensively on a plotter.
They are bulky machines, and as the size of paper used in commercial plotters quite often comes to A1 or A0, the actual plotter device has to be mounted on quite a tall stand, and be physically quite wide to hold the 
lengthy bar for the drawing head to move up and down. This makes them quite expensive, along with the fact that the market for this kind of printer hardware is a specialized group. However, if you’re looking for a printer to plot something like architectural drawings, plotters are your only choice.
