Layer 2 refers to off-chain networks, systems, or technologies built on top of underlying blockchains, known as Layer 1 networks, to enhance their scalability and performance. The key value of Layer 2 solutions lies in leveraging the security of the underlying blockchain; however, sidechains do not qualify as Layer 2 since they maintain independent security mechanisms. Layer 2 addresses the scalability trade-offs faced by blockchains striving for decentralization and security by increasing transaction throughput and reducing costs without compromising these core attributes. The concept, rooted in Vitalik Buterin's "blockchain trilemma," acknowledges the challenge of balancing scalability, security, and decentralization. Emerging technologies like Layer 2 suggest that blockchains face scalability constraints due to excessive tasks, and solutions like payment channels and rollups, including optimistic and zk-rollups, offer promising approaches by delegating transaction execution off-chain while submitting cryptographic proofs to the underlying blockchain for validation. These proofs, crucial for security and decentralization, come in forms like fault proof and validity proof, ensuring transaction integrity and facilitating blockchain expansion. Despite being in early stages, Layer 2 has significant potential to drive Web3 adoption by improving user experience and application development, although further real-world testing is necessary.