> For the complete documentation index, see [llms.txt](https://docs.ackinacki.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.ackinacki.com/for-developers/messages.md).

# Messages

In the Acki NAcki blockchain, a **message** is the fundamental unit of interaction between accounts (contracts). All actions, state changes, and logic execution within accounts are triggered by messages.

### Message types

There are three types of messages in Acki Nacki:

* External incoming: sent from outside the blockchain → received by a smart contract
* Internal: sent from a smart contract → received by a smart contract
* External outgoing: sent from a smart contract → received outside the blockchain

You can learn more at the following link: <https://dev.ackinacki.com/abi/abi#message-body>