Actually, both translating and interpreting aim at rendering the message from the source language to the target language. Both require linguistic competence and knowledge regarding the topic being translated. What makes them different is translation focuses on written texts while interpreting focuses on the oral one. Since the interpretation must be provided on the spot, there’s no chance to consult any dictionary or thesaurus. Everything is spontaneous. Interpreting requires an ability to think quickly (usually under time pressure). The interpretation is presented only once and thus cannot be reviewed or replayed. Meanwhile translation is not as spontaneous as interpreting; the translator has a chance to consult a dictionary or thesaurus and edit his/her work.
Translation rarely requires extraordinary listening abilities since it mostly deals with written texts while interpreting requires extraordinary listening abilities, especially for simultaneous interpreting. In addition, interpreters have to possess excellent public speaking skills, and the intellectual capacity to instantly transform idioms, colloquialisms and other culturally-specific references into analogous statements the target audience will understand.