This glossary defines and explains many LayerZero concepts and terminology.
User Application (UA)
A User Application (UA) is any contract that uses LayerZero to send & receive messages between blockchains. We define UA as a tuple (chainId, contractAddress)
the UA that send() the message at the source chain as srcUA (srcChain, srcAddress)
the UA that lzReceive() at the destination chain as dstUA (dstChain, dstAddress)
In LayerZero's perspective, srcUA and dstUA are different, though they might be the same entity.
Ultra-Light Node (ULN)
ULN is a messaging protocol, firstly introduced in the LayerZero white paper, that allows lightweight cross-chain messaging with configurable trustlessness on the specification of Oracle and Relayer, the two roles that are relaying block information and transaction proof across chains.
A contract address that can be notified to move a block header.
What is a Relayer?
Any process that delivers a transaction proof in the LayerZero system.
The contract that handles the message payload packing on the source chain and verification on the destination chain. Ultra-Light Node is an implementation of Messaging Library
The contract that verifies the validity of a proof. Merkle Patricia Tree inclusion proof is an implementation of Proof Library.