They are introducing a guy, Billy Shears, the "singer" of the band. Many conspiracy theorists see connections to the supposed death of Paul McCartney to that, since the supposed guy replacing him was a guy named William. Worked as a police officer in Canada, won a Paul look-a-like contest. This connects to a line in She Came In Through The Bathroom Window on Abbey Road, "And so I quit the police department, and got myself a steady job." Anyway, I'm rambling.
"So let me introduce to you, the one and only Billy Shears, of Sgt. Pepper's Lonely Hearts Club Band........Biiiiilllllyyy Sheeeeaarrrrs"