Arbitrage in web3 is the practice of exploiting price differences of the same asset across different markets or platforms to make a profit. It's a key factor in Maximal Extractable Value (MEV). Traders, DeFi users, and MEV searchers commonly use this term. To excel in arbitrage, one should understand DeFi protocols, be proficient in writing high-speed trading bots, and have a deep knowledge of blockchain mempool mechanics and gas optimization techniques.