Translator needed on Aisle 4!

Have you ever been in the Atlanta airport and heard a desperate call for a translator? Probably some poor tourist or immigrant is being herded through the documents screening, and he or she doesn't speak a language the security folk can understand.
So the cry goes up for... let's say... "Armenian translator needed at security line 4!"
Nah. They don't need a translator.
What they need is an interpreter.
What's the difference between an interpreter and a translator?
Very simply, a translator deals with written materials, an interpreter with live, spoken language.
If you are in the hospital in a foreign country and you need someone to help you describe your symptoms to the doctor and explain his or her instructions to you, that person will be interpreting your spoken language into the spoken language of the doctor.
If the language professional has to write out the doctor's written instructions to you in your language, she's translating.
Interpreting and translating are very different skills. Both involve a high degree of familiarity with both the language and cultures of the two respective languages (the language pair). But translation can generally be done in the quiet of one's office surrounded by dictionaries and other aids (and let's not forget Google!) whereas interpreting is done on site, sometimes under very difficult circumstances (such as an emergency room), and with few or no language aids.
Interpreters and translators usually charge, too, and there's another difference. Interpreters are likely to charge by the hour, including travel expenses. Translators charge by the word or by the page. You can expect to pay translators more if there is a lot of technical vocabulary involved or for a short turn-around. Both usually have a minimum fee.

Both interpreters and translators work for government, military, industry and non-profit organizations. In fact, many language professionals do both interpreting and translating, when called upon to do so.

In this picture, an American interpreter helps a US Army sergeant communicate with Iraqi women, in order to establish a women's sewing center in Muafiqiyah.  A translator is much more likely to work in a setting like this: