Arbitrum Nitro separates transaction ordering from execution and settlement. A sequencer orders transactions and quickly broadcasts results; execution combines Ethereum-compatible processing with ArbOS functions for fees and cross-chain messages. Compressed batches are published to the parent chain so other participants can reproduce the state. A rollup assertion is a claim about that execution. Under the BoLD dispute system, competing claims can be narrowed to an execution step that an Ethereum contract checks. This is why a sequencer receipt and a confirmed assertion have different meanings.

The ordinary submission path is convenient, but Nitro also has a delayed inbox on the parent chain. A transaction submitted there can become eligible for forced inclusion after the relevant delay. This provides a protocol route around exclusion by the sequencer, while requiring a parent-chain transaction and patience. It does not promise the same price, order, or trading opportunity the user originally wanted. Time-sensitive applications must account for the difference between eventual inclusion and immediate execution.

Arbitrum is also a software family, so an Arbitrum-branded chain is not automatically configured like Arbitrum One. Nitro can support rollup data publication or the AnyTrust committee model, which adds a different data-availability assumption. Similarly, a canonical withdrawal follows the parent-chain assertion and challenge process, whereas another bridge may advance liquidity before that process finishes. Comparing these routes requires checking which contract releases funds and which party bears the delay. Lower execution fees do not remove bridge, application, or upgrade risks.