Layer 2

A layer 2 is a blockchain network built on top of a main chain such as Ethereum that processes transactions more cheaply and quickly, then settles them back to the main chain. The Arbitrum Foundation's glossary describes layer 2 solutions as scaling systems built on Ethereum's base layer that aim to cut transaction costs without adding trust assumptions. The most common kind is a rollup, which ethereum.org's glossary says batches many transactions into a single transaction on the Ethereum main chain. ethereum.org's layer 2 page suggests asking whether a network stores its data on Ethereum, and says each network's safety depends on its technology, smart contract security and maturity.

Layer 2s have hosted large airdrop campaigns. ARB is an ERC-20 token native to the Arbitrum One rollup, and Blast describes itself as an EVM-compatible optimistic rollup where users earned airdrop points by bridging. Tokens are claimed on a specific network, so check which one the project names. See Arbitrum and Blast on AirdropStop.