This stands for "Bluray Rip." It means the video was ripped (copied) from a Blu-ray disc, suggesting it's of high quality.
The film's cinematography, handled by Séamus McGarvey, is notable for its stark, unflinching portrayal of Bill's world. The use of a muted color palette, combined with a stark, modern aesthetic, creates a sense of detachment and isolation. This visual representation of Bill's emotional state effectively conveys the character's feelings of disconnection and shame.