Gossip, or the juicy inside details on a situation. “Spilling the tea” means sharing gossip, and asking “what’s the tea?” is asking someone to fill you in on what’s really going on. It’s less about facts and more about the drama behind them.
Rooted in Black and queer ballroom/drag culture, where “T” was shorthand for “truth”, sharing your “T” meant telling your real, honest story. It crossed into mainstream slang through drag culture, gaining massive momentum after RuPaul’s Drag Race popularized it. By the late 2010s, “tea” had become mainstream internet slang, thanks to social media and meme culture.