A leaderboard is a public ranking of AI models or systems based on their performance on standardized benchmarks. Sites like the Hugging Face Open LLM Leaderboard and LM Arena rank models by scores on tasks like reasoning, coding, and language understanding. Leaderboards drive competition and transparency in AI research, helping developers and businesses compare models objectively. However, optimizing for leaderboard scores can lead to overfitting to benchmarks at the expense of real-world performance.