I would guess that most Bostonians and visitors to town don't give a second thought to Berklee when they pass by its buildings. In my case, however, I took two courses in jazz appreciation at UCLA in the early 1980s as an undergraduate, so I was familiar with Berklee as the alma mater of numerous musicians.
According to this Wikipedia entry on Berklee:
At the time of its founding [1945], almost all music schools focused primarily on classical music. The original mission of Berklee was to provide formal training in jazz, rock, and other contemporary music not available at other music schools.
This emphasis on jazz and rock (including the "fusion" of the two) is illustrated by the following large display on one of the Berklee buildings.
Within jazz, my favorite instrument is the electric guitar. As seen on this list of Berklee alumni, practitioners of this instrument who went to school there include John Abercrombie, Al DiMeola, John Scofied, and Mike Stern. Another jazz guitarist, Pat Metheny, taught at Berklee as a 19-year-old, and later came back to give the commencement address.
Berklee's alumni stretch beyond the aforementioned musical genres, however, to include country. In fact, Dixie Chicks lead vocalist Natalie Maines, from my home base of Lubbock, Texas, received some of her training at Berklee.
