The best way to understand the meaning of bas-relief is to see one—and the easiest way to do that is to look at a penny, nickel, or other coin and examine the raised images on it; they're all bas-reliefs. English speakers adopted bas-relief from French (where bas means "low" and relief means "raised work") during the mid-1600s; earlier, we borrowed the synonymous basso-relievo from Italian. The French and Italian terms have common ancestors (and, in fact, the French word is likely a translation of the Italian), but English speakers apparently borrowed the two independently. Bas-relief is more prevalent in English today, although the Italian-derived term has not disappeared completely from the language.