Sans serif

In typography, a sans serif typeface is one that does not have the tiny feet called "serifs" at the end of strokes. 
The term comes from the French word "sans", meaning "without" and "serif" from the Dutch word "schreef" meaning "line".
Sans serif typefaces have been used since the 18th century, but became most used in the twentieth century as the modern art movement developed. Most designers of typefaces were artists. Some were outstanding in other artistic fields, and were part of the wider artistic culture of their times.
The apostle of sans serif was Jan Tschichold (2 April 1902 Leipzig, Germany – 11 August 1974 Locarno, Switzerland), a German-Swiss graphic designer. 
Tschichold not only designed typefaces, he showed how they could be used in the design of book printing. He was a chief designer for Penguin Books after the Second World War.
Sans serif faces are most used for display signs, advertising and for headings in books. Although they seem to work well for the text in books, they are much less used for that purpose.