Conceptually, an Interpreter and a Translator share the same responsibility, which is to take the words of one language and render it in another so that it can be understood by an audience that is unfamiliar with the original language. Because of this, sometimes the terms interpreter and translator are interchanged, although it’s not actually correct to do that.
While the general principle is the same, the actual mechanics and method between the two professions is quite different. The most obvious differentiator is medium. Interpreters work in real time with the spoken word. Someone speaks in their native language and the Interpreter must then, very quickly, paraphrase what was said in some other “target” language. A Translator on the other hand, reads text in its original language and then takes the time to rewrite it in a new target language, taking the time to ensure that the original intent of the writing is preserved while the actual writing itself feels natural and reads fluently to audiences of the target language.
Interpreters must have the ability to think quickly on the spot, since they don’t know what their speaker is going to say, and, unlike a Translator, they don’t have the time to refer to dictionaries, grammar or stylebooks in order to ensure maximum eloquence. Also, in a radical difference from Translators, they may sometimes be required for two-way communication. That is, an actual conversation or exchange of information may be required between two parties that speak different languages. Not only must the Interpreter be able to paraphrase from one language, but paraphrase the reply so the original speaker can hear the response. Translators work in a strictly one-way capacity; once the translation is written and submitted, the job is done.
The best way to think of the difference between interpretation and translation is the difference between a mediator and a writer. Mediators work with people, and as such, social skills and the ability to interact with others in a decisive, meaningful way are the most important traits to have. Writers, on the other hand, are expected to craft finely tuned, finished content. Where an Interpreter must simply make sure that a speaker is understood at any given moment, a Translator must take the time to ensure that more than comprehension is present. Translators must adjust the original source material to make it as easily consumed as possible for the new audience, and that can sometimes even mean writing entirely new phrases that merely contain the spirit of the content, rather than exact translation. For example, the use of puns as humor is one area where often a Translator may be forced to use an alternative means of communicating the humor because the reliance in the pun may be one words that sound phonetically similar, but, when literally translated, have no relation at all. Interpreters on the other hand, must have a massive vocabulary on hand, or else occasionally be extremely specialized in a field of study, as an interpretation of high level science talks would require familiarity with scientific principles in addition to language skills.
Both Interpretation and Translation are very important in today’s connected world, but they require very different skill sets and often have very different demands.