# Bank

:::{Important}
Terra's bank module inherits from the Cosmos SDK's [`bank`](https://docs.cosmos.network/master/modules/bank/) module. This document is a stub and covers mainly important Terra-specific notes about how it is used.
:::

The bank module is the base transactional layer of the Terra blockchain. This module allows assets to be sent from one `Account` to another. The bank module defines the following types of send transactions: `MsgSend` and `MsgMultiSend`.

## Message types

### MsgSend

`MsgSend` transfers funds from a source account to a destination account. 

```go
// MsgSend - high level transaction of the coin module
type MsgSend struct {
    FromAddress sdk.AccAddress `json:"from_address"`
    ToAddress   sdk.AccAddress `json:"to_address"`
    Amount      sdk.Coins      `json:"amount"`
}
```

The Bank module is used to send coins from one Terra account to another. `MsgSend` is constructed to facilitate the transfer. If the balance of coins in the sender `Account` is insufficient or the recipient `Account` is unable to receive the funds via the bank module, the transaction fails. Fees already paid through failed transactions are not refunded.

### MsgMultiSend

```go
// MsgMultiSend - high level transaction of the coin module
type Input struct {
  Address sdk.AccAddress `json:"address" yaml:"address"`
  Coins   sdk.Coins      `json:"coins" yaml:"coins"`
}

type Output struct {
  Address sdk.AccAddress `json:"address" yaml:"address"`
  Coins   sdk.Coins      `json:"coins" yaml:"coins"`
}

type MsgMultiSend struct {
  Inputs  []Input  `json:"inputs" yaml:"inputs"`
  Outputs []Output `json:"outputs" yaml:"outputs"`
}
```

To send multiple transactions at once, use `MsgMultiSend`. For each transaction, `Inputs` contains the incoming transactions, and `Outputs` contains the outgoing transactions. The `Inputs` coin balance must exactly match the `Outputs` coin balance. Batching transactions via `MsgMultiSend` conserves gas fees and network bandwidth. Fees already paid through failed transactions are not refunded.

## Parameters

The genesis parameters outlined in the [Genesis Builder Script](https://github.com/terra-money/genesis-tools/blob/main/src/genesis_builder.py#L92) are as follows:

```py

    # Bank: setup supply
    genesis['app_state']['bank']['supply'] = [{
        'denom': DENOM_LUNA,
        'amount': str(TOTAL_ALLOCATION),
    }]

    # Bank: set denom meta
    genesis['app_state']['bank']['denom_metadata'] = [{
        'description': 'The native staking token of Terra 2.0',
        'denom_units': [
            {'denom': 'uluna', 'exponent': 0, 'aliases': ['microluna']},
            {'denom': 'mluna', 'exponent': 3, 'aliases': ['milliluna']},
            {'denom': 'luna', 'exponent': 6, 'aliases': []},
        ],
        'base':    'uluna',
        'display': 'luna',
        'name':    'LUNA',
        'symbol':  'LUNA',
    }]

    ```