A validium uses zero knowledge proofs for transaction validity and stores transaction data off-chain with a central data provider.
Pure validiums represent the cheapest and least secure in this spectrum
Data availability committees (DACs)
Rather than a single provider, a committee is entrusted with providing data availability to the network.
If the committee were to act maliciously, they could freeze or steal all funds on the chain and kill the chain’s liveness entirely.
A Celestium is an L2 chain that leverages Celestia for data availability, but uses Ethereum for settlement and dispute resolution.
The validator set of Celestia is akin to a permissionless DAC but with economic security guarantees in the form of slashing.
Rollups that leverage Ethereum’s on-chain data availability inherit the highest DA guarantee at the highest cost.
For users that desire lower cost, other off-chain DA options will be available, including Celestiums.