Pinyin is the romanization system used both inside and outside china for Mandarin Chinese. Other online translators incorporate pinyin as part of their translations.
The key utility of providing pinyin as part of translations is that it will provide users with the pronunciation and corresponding tones that they need. Written Chinese is not based on an alphabetical system, rather it is based on a character system. While meaning can be discerned from radicals within characters, pronunciation is not readily apparent. Thus while a correct translation may be provided to the user, it is functionally unintelligible to the user unless they use a character dictionary or look up the pronunciation elsewhere.
