Layer-1 and Layer-2 blockchains are two approaches to processing transactions and supporting decentralized applications, but they operate at different levels. A Layer-1 blockchain is the main, underlying blockchain network itself. It handles transaction validation, consensus, security, and settlement directly on its own network. Examples include Bitcoin, Ethereum, and Solana. Layer-1 networks typically have their own native tokens, which may be used for transaction fees, staking, or network participation.

A Layer-2 blockchain, in contrast, is a secondary network or protocol built on top of an existing Layer-1 blockchain. Its primary purpose is to improve scalability by processing transactions away from the main chain and then recording or settling relevant information back on Layer-1. This can help increase transaction speeds and reduce fees while still benefiting from the security of the underlying network. Examples include Arbitrum and Optimism, which are Layer-2 solutions designed for Ethereum.

The main difference is therefore their role. Layer-1 provides the foundational infrastructure and establishes the blockchain's core security and consensus, while Layer-2 focuses mainly on scaling and improving the efficiency of that foundation.

Layer-1 networks can face congestion when transaction demand becomes high, potentially increasing fees and confirmation times. Layer-2 solutions attempt to address these limitations by handling transactions more efficiently.

Both layers are important to blockchain development. Layer-1 provides the foundation, while Layer-2 can expand transaction capacity and make blockchain applications more practical for larger numbers of users.