Pappardelle is a wider version of fettucine (or tagliatelle). It originates in Emilia-Romagna (Italy) and typically could be sauced with a wild boar or duck ragu or rabbit. Bolognese would also work, although tagliatelle is better with that.

Pappardelle is a shape of pasta, as far as I know. It's a thicker version of fettuccine. In other words, I dont think there is such a thing as pappardelle sauce; instead, you would serve pappardelle with a sauce of your choice.