Short answers, pulled from the story.
The first written record of the word jazz appeared in 1912 when a minor league baseball pitcher in Los Angeles described a wobbly pitch as a jazz ball. The term later appeared in a Chicago newspaper by 1915 and was used by the New Orleans Times-Picayune to describe jas bands in 1916.
The roots of jazz lie in the gatherings at Congo Square in New Orleans where slaves practiced their culture and played drums on Sundays until 1843. These gatherings featured African-based dances and rhythms that survived despite the Black Codes outlawing drumming by slaves in the South.
The Original Dixieland Jass Band made the first jazz recordings in early 1917 and released Livery Stable Blues which became the earliest released jazz record. While the music originated in African-American communities the first recordings were made by a white band.
A new style known as bebop emerged in New York City in the early 1940s and shifted jazz from danceable popular music toward a more challenging musician's music. Key figures included saxophonist Charlie Parker pianists Bud Powell and Thelonious Monk trumpeter Dizzy Gillespie and drummer Max Roach.
Miles Davis introduced the concept of modal jazz to the greater jazz world with his 1959 album Kind of Blue which became the best-selling jazz album of all time. The album was composed as a series of modal sketches where musicians were given scales that defined the parameters of their improvisation.
Free jazz and the related form of avant-garde jazz broke through into an open space of free tonality in which meter beat and formal symmetry all disappeared. This style explored playing without regular meter beat and formal structures drawing from a range of world music from India to Africa.