A message is an object that contains some data that when broadcast to the network, can change the state of the blockchain. This can include sending tokens, creating a new account, or deploying a smart contract. Messages are signed by a sender and broadcast to the network. This message is then verified and included in a block.
This is the general structure of a Message object:
/**
* A Fuel message
*/
export type Message = {
messageId: BytesLike;
sender: AbstractAddress;
recipient: AbstractAddress;
nonce: BytesLike;
amount: BN;
data: BytesLike;
daHeight: BN;
};