Translation is the action of interpretation of the meaning of a text, and subsequent production of an equivalent text, also called a translation, that communicates the same message in another language. The text to be translated is called the “source text,” and the language it is to be translated into is called the “target language”; the final product is sometimes called the “target text.”

Translation must take into account constraints that include context, the rules of grammar of the two languages, their writing conventions, and their idioms. A common misconception is that there exists a simple “word-for-word” correspondence between any two languages, and that translation is a straightforward mechanical process. A word-for-word translation does not take into account context, grammar, conventions, and idioms. The art of translation is as old as written literature. Interpreting, or “interpretation,” is the intellectual activity that consists of facilitating oral or sign-language communication, either simultaneously or consecutively, between two or among three or more speakers who are not speaking, or signing, the same language.

The words “interpreting” and “interpretation” both can be used to refer to this activity; the word “interpreting” is commonly used in the profession and in the translation-studies field to avoid confusion with other meanings of the word “interpretation.” Not all languages employ, as English does, two separate words to denote the activities of written and live-communication (oral or sign-language) translators.

Source: http://en.wikipedia.org/wiki/Translation