Ragù is in essence an Italian version of stew, made with a meat and vegetables. The meat can be beef, lamb, chicken, veal, pork etc. I have a wonderful memory of being in a small family run restaurant in a tiny town in Tuscany with my wife and then 1 year old son, and enjoying a ragù made with wild boar over a homemade pappardelle pasta. Allegedly the bore had been hunted a couple of days before and cooked the previous day. Even if not true it gave the experience an added dynamic of a proper Italian country style home cooked meal.
I can't quite remember how this particular recipe ended up in our kitchen, probably an early attempt at giving a lamb stew an Italian feel to it by adding the sausage. The key here I think is the cooking time. Although it can be ready in about an hour, it really gets so much better when cooked longer. The flavours become more pronounced and the meat starts to fall apart and the sauce becomes so much richer. As a pasta sauce ragù does differs from normal tomato based pasta sauces as the focus is the meat rather than the tomatoes. In this particular version I also don't add in to many other vegetables, however you can add in some carrot and celery if you wish.