It is just a drawing made with ink, most of the times with Chinese or Indian ink. The traditionally drawing is created with steel, copper or brass nib on a paper sheet. These type of nibs are also used for calligraphy. Many cartoon artists use nibs in order to make their cartoons or comic strips.
As a good example of these type of drawing you can see illustrations by Gustave Dore, Jan Marcin Szancer or cartoon artist Will Eisner who actually used both nib and pencil (i.e. the very fine brush).
Nowadays many artists use also fine-liners, genuine pens, rapidographs, self-made wooden nibs, etc. So, the technique is not limited to certain tools used. It is up to the artist what one uses.
