What do the letters in the bar CBGB’s name stand for?

Country, Bluegrass, and Blues

Country, BlueGrass, Blues, & Other Music For Uplifting Gourmandizers.”

. . . which were the styles of music that owner/founder Hilly Kristal intended to feature there. He was as surprised as anyone when his club became the birthplace of punk, as it were.

CBGB actually has a website at http://www.cbgb.com which contains Kristal’s history of the club. Another good reference is the book Please Kill Me: The Uncensored Oral History of Punk by Legs McNeil and Gillian McCain.