Pears are the fruit of a flowering tree in the genus Pyrus, which is in the rose family. It probably originated in China nearly 3,000 years ago, and was certainly known to the ancient Greeks and Romans (who did not eat it raw). While there are hundreds of varieties in dozens of subspecies, most of the common supermarket pears are of the species communis. Pears are related to both the apple and the quince.
Pear trees are of medium height, and often are grafted to promote better fruit production. Pear leaves are glossy green on top and sometimes have a downy silver underside. Pear blossoms are creamy white, sometimes with a pink or yellow shading. The trees are often used in ornamental applications. Pear wood is used in carving, furniture, and for making musical instruments.
The fruit of the pear is classically 'pear-shaped', tapered a bit toward the top and more bulbous on the bottom. Pears typically have green, yellow or red skins, and some varieties that are green or yellow may have a blush to them. Color is not an accurate indicator of ripeness -- the best way to tell a ripe pear is to press gently on the tapered neck. If it gives to slight pressure and has a sweet, aromatic aroma, the pear is ripe. Pears will ripen once picked by leaving them at room temperature, which can be accelerated by placing them in a paper bag or near bananas. Interestingly enough, pears that are over-ripe tend to smell strongly of banana.
The characteristic aroma of pear is mainly a chemical called isoamyl acetate, which smells like "pear drops", a common British candy. Isoamyl acetate in a high enough concentration smells like banana.
While there are some varieties of pear that retain a bit of crunch when ripe, most varieties of pear are tender and soft, with a slightly gritty texture from stone cells (which are really sclereids - a support structure in plants). Pears can be eaten out of hand, but are often poached in wine or caramelized for desserts. Pears can be sliced and dried as well.
Pears have been used to make hard cider for centuries. Typically known as "perry", this alcoholic beverage is traditionally made in Normandy, but also in the English counties of Worcestershire, Gloucestershire, and Herefordshire. Pears contain sorbitol, an unfermentable sugar (which is also a laxative!), which passes through fermentation, leaving perry naturally sweet. Perry is also distilled into pear brandy (often called Pear Williams), an eau de vie.
In cocktail usage, pears are typically either used as garnish or muddled into drinks for their texture and musky-sweet aroma and flavor.