A rollup executes a sequence of user operations outside its settlement chain and submits commitments together with the data and verification material required by its design. The settlement chain enforces rules for accepting the resulting state. Rollups aim to share settlement costs across many operations rather than executing every operation directly on the base layer. Publishing sufficient reconstruction data is central: posting only an unexplained state hash or proof does not by itself make all off-chain activity reconstructible.

A typical user first sees acceptance from a sequencer, then inclusion in the rollup's own history, and later publication and acceptance on the settlement chain. These observations can occur at different times. For example, a wallet might show a successful transfer before its batch has reached the base layer. A careful application labels that intermediate status rather than presenting the sequencer's response as identical to finalized settlement. Bridge withdrawals can add another workflow with its own verification and timing.

Optimistic designs use dispute mechanisms, while validity-proof designs demonstrate acceptable state transitions through proofs. Both still need a working data-availability strategy. Other material questions include who can sequence transactions, submit proofs or challenges, upgrade contracts, and trigger emergency controls. Those details vary by deployment and can change. Research a named rollup using its actual contracts and current documentation; the category alone does not establish decentralized operation, immediate withdrawals, or freedom from administrative trust assumptions.