Some vocabulary analysis about ZetaChain

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Externally Managed Vault/Assets
The ZetaChain validator set can manage vaults on connected chains just as an account on that chain can, through its TSS architecture. This functionality allows even non-smart-contract chains like Bitcoin to be managed by contracts on ZetaChain.

Hyper-Connected Node
ZetaChain's node observes and processes transactions from all connected chains. By being "hyper-connected" the node is able to support chain-agnostic observation and thus interoperability.

Interface Contract
Smart contracts on connected chains like Ethereum or Arbitrum interact with ZetaChain by passing/receiving messages from ZetaChain's Interface Contracts, which are deployed on each connected chain. This makes

Multichain
Blanket term for apps or concepts that span multiple blockchains.

Observer
The observers watch externally connected chains for certain relevant transactions/events/states at particular addresses via their full nodes of external chains. The observers can be further divided into two roles: sequencer and verifier. The sequencer discovers relevant external transactions/events/states and reports to verifiers; the verifiers verify and vote on ZetaChain to reach consensus. The system requires at least one sequencer and multiple verifiers. The sequencer does not need to be trusted, but at least one honest sequencer is needed for liveness.

Omnichain
As if all blockchains or layers were connected into a single chain. ZetaChain is an 'omnichain' solution, since it is chain-agnostic and allows interoperability between all connected chains.

Omnichain messaging
Messaging value and/or data between chains seamlessly (via ZetaChain).

Omnichain smart contracts
ZetaChain's native smart contracts are omnichain, meaning that they can manage, read, and write state to/from external chains. These smart contracts are the first of their kind, and unlock a new paradigm of dApps that transcend individual chains and layers.

Revert
During a cross-chain transaction, the case that a destination transaction fails (insufficient funds sent, unforeseen changes on the destination, etc.) ZetaChain is capable of reverting the transaction and returning funds to the sender on the source chain.

Signer
The ZetaChain collectively holds standard ECDSA/EdDSA keys for authenticated interaction with external chains. The keys are distributed among multiple signers in such a way that only a super majority of them can sign on behalf of the ZetaChain. Its important to ensure that at no time is any single entity or small fraction of nodes able to sign messages on behalf of ZetaChain on external chains. The ZetaChain system uses bonded stakes and positive/negative incentives to ensure economic safety

TSS
Threshold Signature Scheme. To avoid any single point of failure, ZetaChain uses state-of-the-art multi-party threshold signature scheme (TSS) (see whitepaper for more details). To the outside world, the ZetaChain validators collectively possess a single ECDSA/EdDSA private key, public key, and address, and the signature signed by ZetaChain can be verified efficiently and natively by standard ECDSA/EdDSA verification procedure by the connected blockchains. Internally, the private key is generated without a dealer, and the private key is distributed in all the validators. At no time is a single entity or a minority of validators able to piece together the private key and sign messages on behalf of the whole network. The key generation and signing procedures are done by Multi-Party Computation (MPC) which reveal no secret of any participating node. Because ZetaChain can hold a TSS key and address, ZetaChain can support smart contracts that can manage native vaults/pools on connected chains including Bitcoin. This effectively adds smart contract capabilities to the Bitcoin network, and potentially other non-smart contract blockchains. The TSS employed by ZetaChain gives the performance and convenience of hot wallet with cold wallet level security.

Validator
ZetaChain uses the Tendermint consensus protocol which is a partially synchronous Byzantine Fault Tolerant (BFT) consensus algorithm. Each validator node can vote on block proposals with voting power proportional to the staking coins (ZETA) bonded. Each validator is identified by its consensus public key. Validators need to be online all the time, ready to participate in the constantly growing block production. In exchange for their service, validators will receive block rewards, and potentially other rewards such as gas fees or processing fees, proportional to their bonded staking coins.