The Chinese language, a Sino-Tibetan language, consists of variety of branches mutually intelligbe to varying degrees. About one-fifth of the world's population, or over one billion people, speaks some variety of Chinese as their native language.
Standard Chinese (Mandarin) is the official language of the People's Republic of China (mainland), Republic of China (Taiwan), and one of the official languages of Singapore. It's one of the six working languages of the United Nations
Pinyin is the phonetic system, which transcribes the sounds of Mandarin into Roman alphabet. Pinyin is used for help to make a correct pronunciation of characters in Mandarin, and is used to input Chinese characters through keyboard.
Chinese Characters are the written form of Chinese words. One characters represents a single syllable. There are about 80,000 Chinese characters, however, in the modern time today, a couple of thousands will be enough for basic reading and writing. According to published Chinese government data, 2500 most frequently used characters have 99% coverage rate.