The nashi doesn't come in the typical pear shape - it looks more like an apple, which explains why it's also called the apple-pear. Another common name for it is Asian pear, because the fruit is grown in parts of East Asia.
In taste and texture, the apple-pear has similarities to both fruits, and differences. It's crisp, like many types of apple, and grainy, like certain varieties of pear, but it's also very juicy, with a wonderfully snappy bite. The skin of the fruit is quite tough, so it's usually peeled before being eaten. It's an expensive fruit (compared with most apples and pears) so it's often sold wrapped in protective netting. When buying a nashi pear, pick it up and weigh it in your hand - it should feel hefty, and the skin should be taut over the flesh, without wrinkles. In general, the larger fruits are much more expensive than the smaller ones.
The nashi pear is delicious unadorned - peel it and, after removing the core, cut it into thick wedges. It's also used in marinades and salad dressings, although it's probably better (and more economical) to use the smaller nashi pears; after all, there's no need for fancy fruit when you're just going to puree it. For a Korean marinade for barbecued beef, puree nashi pear (peeled and cored) with onion, peeled ginger and garlic cloves in a food processor or blender, then add soy sauce, rice wine and sesame oil. Massage this into the beef and leave for about 30 minutes, mixing occasionally, or longer if the meat is thickly sliced. Drain the meat before grilling it. Because of the sugar in the nashi pear and soy sauce, the meat will caramelise beautifully.