Disclaimer: In some instances, Wormhole uses general terms for decentralized, cross-chain elements as branded verbiage. In most casese, the definition of the general term does not differ from Wormhole's definition though Wormhole's definitions may be more narrow than general interpretations.
Guardian - One of the 19 validators in the Guardian Network that contributes to the VAA multisig.
Guardian Network - Validators that exist in their own p2p network that serve as Wormhole's oracle by observing activity on-chain and generating signed messages attesting to that activity.
Relayer - Any process which delivers VAAs to a destination.
VAA - Verifiable Action Approvals (VAAs) are the key piece of data in the Wormhole ecosystem, containing the messages emitted by xDapps along with information such as what contract emitted the message. The VAAs are signed by the Guardians and need 13/19 signatures to be considered authentic.
Wormchain - A purpose-built cosmos blockchain which aids the Guardian Network and allows for formal interaction with the Guardians.
xAssets - Chain-and-path agnostic token that exists on a layer outside the blockchain ecosystem, which can be used to conduct transactions on any blockchain. There are currently two implemented modules: (1) Token Bridge Module and (2) NFT Bridge Module
xChain - Term that refers to the full range of cross-blockchain interoperability.
xDapp - Decentralized application that enables users to create and/or use xData.
xData - Data that exists in a layer outside of Layer 1 blockchains, which is accessible by all chains.