If by chance you are going to 92Y Tribeca tonight to see a night of heavy-duty cinematic art rock from Sian Alice Group, Mountains, Lights and Zs, the L would like you to know that you should buy your tickets online via the venue's website, and enter the promo code LPBR.
LPBR is an acronym that stands for "L PBR."
What this means is that, because you read The L, you are entitled to free PBR, from 8:30-9:30pm. PBR, of course, is also an acronym. It stands for "Pabst Blue Ribbon."
L does not stand for anything, as far as I know.