L-2, or L2, refers to the second layer of the Ethereum blockchain, designed to improve scalability and transaction speed. It operates on top of the main blockchain, allowing for faster processing of transactions while reducing costs. L-2 solutions, such as Optimistic Rollups and ZK-Rollups, bundle multiple transactions together before submitting them to the main chain. This method helps alleviate congestion on the primary network, making it more efficient for users and developers alike.