谈论 (tán lùn) means 'to discuss, to talk about' — it's the general verb for discussing a topic. Unlike 讨论 (tǎo lùn), which implies a structured or deliberate exchange of opinions (often in a formal setting), 谈论 is more casual and can be used for everyday, free-flowing conversation. It also covers a wider range than 谈 (tán), which simply means 'to talk' without focusing on a specific topic.