B-stage
A B-stage is a small, secondary stage, featured at pop and rock concerts held in arenas and stadiums, and is usually located in the middle of the concert floor, connected to the main stage by a catwalk.
Origins
The B-stage was originally used in the early 1990s by U2 on their Zoo TV Tour. It provided a more intimate setting for stripped-down, quieter versions of songs, that could be played in greater proximity to the audience.
Current examples
B-stages are still commonly used, having become a standard feature of large rock and pop concerts.
Britney Spears
Britney Spears has used a B-stage on her 2001-02 Dream Within A Dream Tour. In the Dream Within A Dream Tour she would use a mini helicopter to get to the B-stage.
Madonna
Madonna has used a B-stage in four of her nine tours starting with Girlie Show, Confessions tour, Sticky and Sweet tour and Mdna tour, connected by a catwalk. In Mdna she has employed a "V" catwalk to connect the main stage with the B stage.
Aerosmith and Bon Jovi
Aerosmith has employed a B-stage on almost every tour since 2001 (sometimes connected by a catwalk). During their outdoor amphitheater performances from 2001–2003, Aerosmith would play three songs on this stage during the middle of the show, and in more recent years, the band members go back and forth between the main stage and the B-stage throughout their performances via a catwalk. Bon Jovi made use of such a stage during their 2008 Lost Highway Tour in which Jon Bon Jovi (and sometimes Richie Sambora) would sing ballads such as "Bed of Roses", "Always", or "Living in Sin" from a smaller stage closer to the crowd, while the rest of the band performed on the main stage.
Mariah Carey and Backstreet Boys
Mariah Carey also used a B-Stage in her The Adventures of Mimi Tour. Backstreet Boys employed a B-stage on their Black & Blue Tour in 2001, playing several ballads from the small circular stage in the middle of the audience. The band appeared on the B-stage via a platform in the center that raised the band from beneath the stage after a blackout and segue video which concealed their travel to the B-stage. They returned to the main stage during the final B-stage song on a bridge over the audience that descended from the rafters, and was raised again after the song.
Beyoncé and Coldplay
Beyoncé has used a B-Stage on every tour since her 2009 I Am... World Tour, in the middle of her show she appears from under the stage wrapped in a harness and taken up and over the audience where she performs "Baby Boy", she then runs through the audience back to the main stage performing "Say My Name". During The Mrs. Carter Show World Tour in 2013/2014 her "BeyStage" included two VIP pit sections with a catwalk in the middle. She also used a B-stage during her 2014 On the Run Tour with Jay Z.
During their 2008/2009 Viva la Vida Tour, Coldplay made use of a B-stage and a C-Stage at different points in each show. The B-stage, located at the end of a catwalk, attached to the main stage, was used in the middle of the set to perform a remix of "God Put a Smile Upon Your Face" and "Talk", as well as a piano version of "The Hardest Part". The C-stage was used at the end of the main setlist to perform three songs acoustically, and was located at the back of venue, in the audience.
Other examples
In their 2009 Out of Control Tour, Girls Aloud had a B-Stage, and during the middle of the show they would get on a moving platform and fly over the crowd to the B-stage for a few songs and then get back on the moving platform to go back to the main stage.
Powderfinger used a B-stage on their 2010 Sunsets Farewell Tour, located at the back of the venue. Midway through the show, the band would leave the main stage and make their way to the B-stage while historical video footage played out on the main video screen. The clip ended with a boxer "punching" the camera, alluding to the video of the song "Like a Dog", which they would then perform on the B-stage. The band would perform another song, then return to the main stage.