As we mentioned above, Layer 2 is a collective term for Ethereum scaling solutions that handle transactions off Ethereum layer 1 while still taking advantage of the robust decentralized security of Ethereum layer 1. A layer 2 is a separate blockchain that extends Ethereum. How does that work?

A layer 2 blockchain regularly communicates with Ethereum (by submitting bundles of transactions) in order to ensure it has similar security and decentralization guarantees. All this requires no changes to the layer 1 protocol (Ethereum). This lets layer 1 handle security, data availability, and decentralization, while layer 2s handles scaling. Layer 2s take the transactional burden away from the layer 1 and post finalized proofs back to the layer 1. By removing this transaction load from layer 1, the base layer becomes less congested, and everything becomes more scalable.