A Layer 2 solution is a secondary framework built on top of a Layer 1 blockchain to improve scalability and speed without compromising the main network’s security. Examples include Lightning Network (for Bitcoin) and Optimism (for Ethereum). Layer 2s handle transactions off-chain and settle them on-chain later, reducing congestion and gas fees. They’re essential for mass adoption because they make blockchain technologies more usable, cheaper, and faster for everyday applications.