Bottle openers come in two main varieties, those intended to remove bottle caps from soda, beer, or water bottles, and those made to remove corks from wine. Both are referred to as bottle openers, but they differ drastically.
A standard bottle opener is simply a lever to wedge beneath the edge of a bottle cap and pry it off the bottle. Most restaurants and bars have a version of this standard opener attached to a wall, so that a bottle can be inserted beneath the opener and pried to remove the cap. Handheld openers are functionally the same as these wall-mounted varieties, but are held in the hand and levered while the bottle is held stationary.
Cap bottle openers come in a wide range of visual styles, many with a fun and entertaining in appearance. Practically, however, they are virtually all the same. Automatic bottle openers are an exception to this. While they are similar to traditional openers, they are housed in a round plastic tubing and designed so that the tube may be simply placed over the bottle and lifted. Automatic bottle openers are touted as being ideal for when one is too drunk to easily use a standard opener.
In the world of wine there are two main styles of bottle opener. The first is a corkscrew, which uses a single screw inserted into the cork and rotated down until it has sufficient grip to allow the cork to be pulled from the bottle. A variant on this style of corkscrew includes side levers which hold the bottle steady and an added lever to allow for a straighter pull. Many restaurants also have a fixed corkscrew with a lever to ensure quick and clean removal of corks.
The other common style of bottle opener for wine consists of two fairly rigid prongs. Rather than piercing the cork to pull it out, the prongs are wedged between either side of the cork and the bottle edge. The friction created may be used to rotate the cork out of the bottle easily and deftly. This style of corkscrew takes some getting used to, and for many people it may take weeks to be able to use it successfully. Once mastered, however, it drastically reduces the chances of a damaged or dropped cork.