Horizontal blockchain scalability fundamentally requires multiple [chains](https://www.notion.so/Longform-technical-explainer-for-Superchain-5d8ced37a3e44d71a4b09d28c16358b6). This is because the hardware requirements to sync a chain increase linearly with the amount of compute the chain performs. Therefore, to achieve horizontal scalability we must run chains in parallel.
Horizontal blockchain scalability fundamentally requires multiple chains. This is because the hardware requirements to sync a chain increase linearly with the amount of compute the chain performs. Therefore, to achieve horizontal scalability we must run chains in parallel.
::: details chains
::: details chains
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Stay Optimistic 🔴✨
Stay Optimistic 🔴✨
## Terminology
## Glossary
#### Chain
-**Chain**: A state [transition system](https://en.wikipedia.org/wiki/Transition_system)—consisting of an initial state, a state transition function, and a list of inputs (transactions)—which is cryptographically committed to and can be independently replicated with commodity computer hardware and internet connection.
A state [transition system](https://en.wikipedia.org/wiki/Transition_system)—consisting of an initial state, a state transition function, and a list of inputs (transactions)—which is cryptographically committed to and can be independently replicated with commodity computer hardware and internet connection.
-**Superchain**: A decentralized blockchain platform which consists of many chains that share security and a technology stack (OP Stack). The interoperability and standardization enables individual chains to be treated identically by tools and wallets.
#### Superchain
A decentralized blockchain platform which consists of many chains that share security and a technology stack (OP Stack). The interoperability and standardization enables individual chains to be treated identically by tools and wallets.
#### OP Chain
An individual chain within the Optimism Superchain. All chains, regardless of their specific properties are considered OP Chains if they are officially governed by the Optimism Collective, and therefore part of the Superchain.
#### Superchain Bridge
The L1 bridge contracts which govern all OP Chains in the Superchain. This bridge can be upgraded by the Optimism Collective.
#### Sequencer
The specific entity or smart contract which has priority when submitting transactions to an OP Chain.
#### Modular Sequencing
The ability to configure the sequencer address during OP Chain deployment. This value can be configured by the OP Chain deployer.
#### Withdrawal Claim
A claim about the state of one chain made on another chain. For instance, I can claim that in OP Mainnet I have burned my tokens with the intent to withdraw those tokens back to L1.
#### Chain Proof
Difficult to forge evidence of the validity of a particular withdrawal claim. Proofs are commonly used to enable chains to communicate with each other.
#### Modular Proof
The ability to use multiple proof systems for the same OP Chain. For instance, it should be possible to prove an OP Chain using a fault proof or a validity proof.
#### Fault Proof
A proof which relies on the absence of counter-evidence to prove correctness.
#### Challenge Period
The window of time in which a challenge can be made to disprove a fault proof.
-**OP Chain**: An individual chain within the Optimism Superchain. All chains, regardless of their specific properties are considered OP Chains if they are officially governed by the Optimism Collective, and therefore part of the Superchain.
#### Attestation Proof
-**Superchain Bridge**: The L1 bridge contracts which govern all OP Chains in the Superchain. This bridge can be upgraded by the Optimism Collective.
A proof which consists of some number of signatures from a pre-agreed upon set of chain attestors.
-**Sequencer**: The specific entity or smart contract which has priority when submitting transactions to an OP Chain.
#### Attestation-Based Fault Proof
-**Modular Sequencing**: The ability to configure the sequencer address during OP Chain deployment. This value can be configured by the OP Chain deployer.
A fault proof where challenges can be successfully made by supplying an attestation proof which disagrees with the original withdrawal claim.
-**Withdrawal Claim**: A claim about the state of one chain made on another chain. For instance, I can claim that in OP Mainnet I have burned my tokens with the intent to withdraw those tokens back to L1.
#### Cannon Fault Proof
-**Chain Proof**: Difficult to forge evidence of the validity of a particular withdrawal claim. Proofs are commonly used to enable chains to communicate with each other.
A fault proof where challenges are evaluated using an on-chain game which is guaranteed to result in a truthful outcome, given economic rationality assumptions.
-**Modular Proof**: The ability to use multiple proof systems for the same OP Chain. For instance, it should be possible to prove an OP Chain using a fault proof or a validity proof.
#### Validity Proof
-**Fault Proof**: A proof which relies on the absence of counter-evidence to prove correctness.
A proof of a withdrawal claim which can be immediately validated, without a challenge period.
-**Challenge Period**: The window of time in which a challenge can be made to disprove a fault proof.
#### Attestation-Based Validity Proof
-**Attestation Proof**: A proof which consists of some number of signatures from a pre-agreed upon set of chain attestors.
A validity proof which can be verified by supplying an attestation proof which agrees with the withdrawal claim.
-**Attestation-Based Fault Proof**: A fault proof where challenges can be successfully made by supplying an attestation proof which disagrees with the original withdrawal claim.
#### Zero Knowledge Proof
-**Cannon Fault Proof**: A fault proof where challenges are evaluated using an on-chain game which is guaranteed to result in a truthful outcome, given economic rationality assumptions.
A validity proof which relies on cryptographic properties and low error margins.
-**Validity Proof**: A proof of a withdrawal claim which can be immediately validated, without a challenge period.
#### Rollup Chain
-**Attestation-Based Validity Proof**: A validity proof which can be verified by supplying an attestation proof which agrees with the withdrawal claim.
A chain where all transaction data is submitted to L1.
-**Zero Knowledge Proof**: A validity proof which relies on cryptographic properties and low error margins.
#### Plasma Chain
-**Rollup Chain**: A chain where all transaction data is submitted to L1.
A chain where transaction data is committed to on L1 but not supplied to L1 directly, with a data availability challenge fallback.
-**Plasma Chain**: A chain where transaction data is committed to on L1 but not supplied to L1 directly, with a data availability challenge fallback.
