According to Britannica, hertz are units of frequency, so 50 Hz contains less frequency than 60 Hz. These units are used to calculate electric currents, electromagnetic waves and sound.
One hertz is equal to one cycle per second. Around the world, different countries utilize different frequencies or cycles. According to PowerStream, as of April 2014, the United States uses 60 Hz with 120 volts. In contrast, most countries in Europe use 50 Hz with mostly 220 volts. These differences arise from not only different metrics used, but also different costs in conversion. In the US, Nikola Tesla believed 60 Hz to be most efficient due to its speed. Countries such as Brazil and Japan cannot decide on a standard frequency, but about 20 percent of the world uses 60 Hz, as of 2014.
Hertz are part of the International System of Units and were adopted in October 1933 by an international committee. The unit's namesake comes from 19th century German physicist Heinrich Hertz. His discovery of radio wavelengths in 1887 brought him critical acclaim and proved James Clerk Maxwell's theory of electromagnetism. The findings were published in Hertz's first book, "Investigations on the Propagation of Electrical Energy." Applications from his discovery are seen in radio broadcasting and radar technology.