A plotter, for example the VIC-1520 with ALPS mechanism, is a device that draws computer graphics on paper using pens mounted on rails. A second variant is the drum plotter, which has 4 pins in a kind of revolving drum. These pens were available as fiber pens and ballpoint pens.
The advantage of this device compared to a printer is the good resolution and especially the precision, which was already about 0.1 mm with old devices. The second advantage was that these were the first color printers. The main disadvantage is the very low printing speed and that you could not print areas so well with plotters. Plotters were primarily intended for technical drawings, as the typeface usually looked very scrawly.