Της αρέσει ο καφές could mean either: she likes coffee in general, or she likes "the coffee" (a particular serving of coffee which the listener will recognise, as it's been mentioned before or is otherwise obvious from context).

Raleigh, what Philip says isn't rare in European languages, btw. Most Romance ones, and perhaps Germanic, would be the same. Seems to rarely cause confusion. This comes up often also with conceptual nouns like freedom, virtue, comprehension, laziness, pride, etc., that take a definite article in many languages.