Short answers, pulled from the story.
A hi-hat is a combination of two cymbals and a foot pedal mounted on a metal stand, used in drum kits across rock, pop, jazz, and blues. Pressing the pedal brings the top cymbal down onto the fixed bottom cymbal, producing a closed "chick" sound. Releasing the pedal lets the cymbals hang apart so they ring when struck with a stick.
The raised hi-hat may have been developed around 1926 by Barney Walberg of the drum accessory company Walberg and Auge. Kaiser Marshall is also named among those thought to have contributed to its invention. The instrument evolved from earlier devices called clangers, shoes, and the Low-boy.
"Papa" Jo Jones is recognized as the first master of the hi-hat. A 2013 Modern Drummer article credited him with shifting jazz time-keeping from the bass drum to the hi-hat and with being the first drummer to use brushes on drums.
A closed hi-hat has the two cymbals pressed together by the foot pedal, producing a short, muted percussive sound called a "chick." An open hi-hat has the pedal released so the cymbals are apart, allowing a shimmering, sustained tone when struck with a stick.
A pedal hi-hat refers to notes played solely by pressing the foot pedal to clash the cymbals together, without striking them with a stick. Jazz drummers commonly use this technique to accent beats 2 and 4.
In hip-hop, the hi-hat is typically played in a simple eighth-note pattern. Rather than a live drummer, this sound is usually produced by a drum machine or by recording a real hi-hat and loading it into a sampler that triggers the sound as programmed.