JB meaning in Community ?

Jazz bass is the use of the double bass or bass guitar to improvise accompaniment ("comping") basslines and solos in a jazz or jazz fusion style. Players began using the double bass in jazz in the 1890s to supply the low-pitched walking basslines that outlined the chord progressions of the songs. From the 1920s and 1930s Swing and big band era, through 1940s Bebop and 1950s Hard Bop, to the 1960s-era "free jazz" movement, the resonant, woody sound of the double bass anchored everything from small jazz combos to large jazz big bands.

Beginning in the early 1950s, some jazz bass players began to use the electric bass guitar in place of the double bass. The electric bass, which was easier to amplify to loud volumes onstage, gained particular prominence in the late 1960s and early 1970s jazz subgenre which blended jazz with the powerfully amplified electric instruments of rock music, creating jazz fusion.

Most jazz bassists specialize in either the double bass or the electric bass, although the ability to "double" (play both instruments) is common. A small number of players, such as Stanley Clarke and John Patitucci, have achieved virtuoso skill on both instruments. Whether a jazz bassist is "comping" (accompanying) with a walking bassline or soloing, or playing on a double bass or an electric bass, they usually aim to create a rhythmic drive and "timefeel" that creates a sense of swing and groove.