An interpreter is someone who translates something to make it understandable, usually spoken language. When your class takes a trip to Russia, you’ll likely have an interpreter to translate Russian to English so you can understand what people are saying to you.
Need to talk to someone who doesn't speak your language? You'll need an interpreter. Say you're interviewing a Bulgarian diplomat, but you don't speak Bulgarian. The interpreter would listen to a few sentences in Bulgarian and then repeat them in English, and then listen to your English response and repeat that in Bulgarian. We also use interpreter for artists who represent ideas or places in their work. If you paint industrial cityscapes, you're an interpreter of urban life.