Trained interpreters use the same grammatical person as the speaker for whom they are interpreting. A subjective question. The ability to interpret simultaneously is not necessarily difficult to acquire. This fact suggests that simultaneous interpretation is not an easy task. Translation normally refers to written materials, i.e, going from one written medium to another.
Interpretation is spontaneous oral translation, from spoken word to spoken word.
Sometimes the term translation is used to mean either one. Court interpreters often sight-translate legal documents like plea agreements. Taping conversations is a frequently used investigative technique. U.S law enforcement agencies and prosecuting authorities often call on translators to transcribe and translate those conversations when they are in a language other than English. By far the most often used language in the U.S. is Spanish, but the courts require dozens of other languages as well.