It has been suggested that this section be split into a new article entitled Romanization of Chinese. (Discuss)
Romanization is the process of transcribing a language in the Latin alphabet. There are many systems of romanization for the Chinese languages; this is due to the complex history of interaction between China and the West, and to the Chinese languages' lack of phonetic transcription until modern times. Chinese is first known to have been written in Latin characters by Western Christian missionaries of the 16th century, but may have been written down by Western travelers or missionaries of earlier periods.
At present, the most common romanization system for Standard Mandarin is Hanyu Pinyin 漢語拼音/汉语拼音, also known simply as Pinyin. Pinyin is the official Mandarin romanization system for the People's Republic of China, and the official one used in Singapore (see also Chinese language romanisation in Singapore). Pinyin is also very commonly used when teaching Mandarin in schools and universities of North America and Europe.
Perhaps the second-most common system of romanization for Mandarin is Wade-Giles. This system was probably the most common system of romanization for Mandarin before Hanyu Pinyin was developed. Wade-Giles is often found in academic use in the U.S., and until recently was widely used in Taiwan (Taipei city now officially uses Hanyu Pinyin and the rest of the island officially uses Tōngyòng Pinyin 通用拼音/通用拼音).
Here are a few examples of Hanyu Pinyin and Wade-Giles, for comparison:
Mandarin Romanization Comparison Characters Wade-Giles Hanyu Pinyin Notes
中国/中國 Chung1-kuo² Zhōngguó "China"
北京 Pei³-ching1 Běijīng Capital of the People's Republic of China
台北 T'ai²-pei³ Táiběi Capital of the Republic of China
毛泽东/毛澤東 Mao² Tse²-tung1 Máo Zédōng Former Communist Chinese leader
蒋介石/蔣介石 Chiang³ Chieh4-shih² Jiǎng Jièshí Former Nationalist Chinese leader
孔子 K'ung³ Tsu³ Kǒng Zǐ "Confucius"
Regardless of system, tone transcription is often left out, either due to difficulties of typesetting or propriety for audience. Wade-Giles' extensive use of easily-forgotten apostrophes adds to the confusion. Thus, most Western readers will be much more familiar with Beijing than they will be with Běijīng, and with Taipei than with T'ai²-pei³.
Regardless of romanization, the words are pronounced the same. Learning a system of romanization requires occasional deviations from the learner's own language, so, for example, Hanyu Pinyin uses "q" for very different values than an English speaker would probably be used to; the sound represented is similar to the English "ch," but pronounced further forward (an aspirated alveolo-palatal fricative, /tɕʰ/). This is a cause of confusion but is unavoidable, as Mandarin (and any language transcribed) will have phonemes different from those of the learner's own. On the other hand, this can be beneficial, since learners can immediately be made aware of the fact that they will have to learn a new pronunciation. With languages that use similar orthography, the temptation to pronounce words just as in one's mother tongue can lead to great misunderstanding.There are many other systems of romanization for Mandarin, as well as systems for Cantonese, Minnan, Hakka, and other Chinese languages.