What is the use of Chromium

What is the use of Chromium? A lot of people are unfamiliar with this stuff, and here's the introduction to it:

Chromium, the chemical symbol Cr, is a steel grey metal. The name of the element comes from Greek, meaning "color" because the compound of chromium has color. In 1797, a French chemist, l. n.v auquelin, discovered a new mineral in the red lead mine in Siberia. The next year, it was reduced to carbon. Chromium in the earth's crust is 0.01% and occupies 17th place. There is no free chromium in nature, mainly in the chromium lead. Ⅵ B clan in the periodic table of elements, chromium atomic number 24, atomic weight of 51.9961, body centered cubic crystal, common valency + 2, + 3 and + 6. The oxidation number is 6, 5, 4, 3, 2, 1, minus 1, minus 2, minus 4, is the hardest metal.