The solution to a boulder or route — which holds, which sequence, which body position.
Beta is the currency of the gym: 'got beta for the red one?' simply asks whether you know how it goes. What matters is that beta is personal — with 15 centimetres of height difference a sequence often stops working entirely, and stubbornly copying a taller climber's solution just blocks you. Etiquette also says don't shout unsolicited beta (spraying beta): plenty of people want to work it out themselves, and working it out is part of the sport. Ask whether someone wants beta before you offer it.