About Layer 2 networks:
ZK Rollups use validity proofs to verify transaction correctness on the mainnet, so withdrawals to the mainnet don't require a one-week challenge period.
Layer 2 is cheap because many transactions are bundled together and submitted to the mainnet, with the mainnet fees shared among them.
$ARB 0.196(+8.05%)

The above is compiled from publicly available information. Please verify it yourself.