This week, Arbitrum overtook Polygon as the Ethereum bridge with the most relative total value locked in at over $2.7 billion and it has remained among the top ranked bridges since. Arbitrum, which was released for public use on August 31, has exploded in popularity due to its unique combination of security, low transaction costs, and Ethereum compatibility.
Arbitrum is Ethereum's first true layer 2 rollup. A rollup is like a sidechain, except it's trustless, permissionless, and non-custodial – the data is still on the Ethereum blockchain and doesn't rely on another blockchain to process and store transactions.
The rollup batches transactions to be recorded later on the Ethereum blockchain. Arbitrum can do this much more efficiently than other projects because the transaction computation and storage of contracts are performed off-chain. A validator then posts the "rollup block" to the Ethereum blockchain. This rollup block contains a record of a batch of transactions. Using this approach, Arbitrum can offer Ethereum transactions with much lower fees while offering better security than Polygon – at least in theory.
Arbitrum does not have a tradable token. There are rumors that an Arbitrum token release is coming in the future, with current users being allotted tokens through an airdrop.