A machine translation system receives as input an arbitrary string in one language and produces, as output, a string with the same meaning but in another language. Google Translate is one example (but also many other main IT companies have their own). There, users are able to translate to and from more than 100 languages. Using the webpage is easy: on the left just put the sentence you want to translate (for example, Hello World), select its language (in the example, it's English), and select the language you want it to be translated to.
Here's an example where we translate the sentence Hello World to French:
Is it easy? At a glance, we may think it's a simple dictionary substitution. Words are chunked, the translation is looked up on the specific English-to-French dictionary, and each word is substituted with its translation....