The translation is done by Google Translate, which is a ‘machine translation’ engine that uses mathematical algorithms when translating. As a result, the translated text is not of the same quality as if it had been translated by a human translator. This also means that there is a difference in quality of translation between the languages.
However, as the technology behind Google Translate improves, the quality of the translation will improve too. Find out more about how Google Translate works on their support page.