The body of a pencil sharpener is usually a shaped piece of plastic, metal or wood. It is shaped with a tapered hole in its centre for inserting a pencil, and above which a sharp metal blade is positioned. The body allows the user to hold the sharpener in a static position while you rotate the pencil. There are grooves along the side of the body that give your fingers a surer grip.
The tapered hole of a sharpener is where you insert the unsharpened or dulled pencil tip. The pencil tip is rotated inside the tapered hole and the blade takes thin shavings off the pencil until it is sharp.
The blade of the sharpener is razor-like with a cutting edge that runs along the length of the tapered hole. The blade is usually affixed to the body of the sharpener by one or two screws. As the pencil rotates inside the tapered hole, the blade shaves off thin pieces of the pencil until it is sharpened to a point.
The screws are simply used to attach the blade to the body of the sharpener. These screws can be undone with a screwdriver and a new blade can be affixed if needed. Packs of new blades are available though these items are quite cheap so buying a new one may be easier.
Not all sharpeners have these, but this particular model has a handy keyring loop at the back of the sharpener so that the user can attach it to a keyring promoting ease of use and quick accessibility. It also reduces the chance of misplacing your sharpener.