Originally Posted by RYM

Bebop is a style of Jazz characterized by fast tempos, improvisation, irregular melodic phrasing, and complex harmonies and chord structures. Inspired by Swing music, bebop was developed in the 1940s and 50s by musicians such as Charlie Parker, Dizzy Gillespie, and Thelonious Monk. Unlike the earlier big bands, these musicians utilized smaller combos and created music less suitable for dancing. Bebop songs typically begin with a melodic "head" but are dominated by extended solo improvisation over a set chord structure. The emphasis is placed on harmonic exploration rather than the catchy melodies of Swing and Big Band. Initially outside the mainstream of Jazz, bebop is now one of its most popular and well-known forms.

Originally Posted by Wikipedia

Bebop or bop is a style of jazz characterized by fast tempo, instrumental virtuosity and improvisation based on the combination of harmonic structure and melody. It was developed in the early and mid-1940s. It first surfaced in musicians' argot some time during the first two years of American involvement in the Second World War. This style of jazz ultimately became synonymous with modern jazz, as either category reached a certain final maturity in the 1960s.