Drum kit

A drum kit (or drum set or trap set) is a collection of instruments played by an individual which is called a drummer.

Setup

A normal drum kit consists of the following:

Bass drum - The largest drum, which is also called a kick drum. It is struck with a hammer that is moved by one's foot.
Snare drum - A drum with small cables of metal wires stretched across the bottom to make the loud "tat" sound. It can also make a "click" sound if hit in a special way.
Tom Toms - Often simply called "toms", there are usually two of these drums across the top of the kit. To the drummer's left (if he/she is right-handed) is the high tom that makes a higher sound; on the other side is the medium or middle tom with a slightly lower sound, depending on the tuning. Sizes tend to range between 10 and 13 inches. The number and positioning varies by the drummer; some drummers have several toms on their kit, such as an 8-inch tom giving an even higher sound (often used in jazz drumming).
Floor Tom - Usually placed to the right of the drummer, this is a tom that has its own legs or stand and produces a lower note than the other toms (usually the second lowest after the bass drum). Sizes tend to range between 14 and 18 inches.
Hi-hat - Two cymbals, usually the same size, that can be pushed together (closed) with a pedal. They can be hit with a drumstick. This sound varies if the hi-hat open, closed, and in-between positions. Another way to play it is to clap the cymbals together with the pedal. The hi-hats are the most important cymbals on the kit, and are often used for detailed timing. Some drummers have more than one hi-hat setup around their kit.
Crash Cymbal - A cymbal that makes a loud "crash" sound. The sound of a crash cymbal varies by brand and product line. The number of crash cymbals depends on the drummer's personal taste and need for the style of music being played. Crash cymbals are very often used to mark the start of a new section of a song.
Ride Cymbal - A large, heavy cymbal that, typically, makes a light, airy sound, named from the fact that the drummer can "ride on it" or keep time on it. It is often used an alternative to the hi-hat. The middle of the ride cymbal is called the bell, and it makes a "ping" sound if hit.

Other cymbals and drums can be added to the setup for a wider range of sounds like the Splash, a small cymbal around 10"/25 cm giving a distinct crash sound with a quick decay, or a China cymbal, that gives an "oriental feel" to beats, rhythms, solos and fills. The latter is much like a crash cymbal popped inside out with the screw and sponge holding it to the stand inside it, so it has a shallow bowl shape.

The drummer can do other things to the kit, such as attach a tambourine to the spine of the hi-hat, so when he/she puts his/her foot down on the pedal or hits it with a drumstick, the drummer gets the tambourine sound at the same time. Cymbals can also have rivets inserted into them to give them a 'sizzling' sound, or a cowbell can be attached to the top of the bass drum between the snare and floor tom to use in fills, solos, grooves, etc.