docs: add doc section for UTXO model (#2624)

.changeset/modern-bugs-exist.md

@@ -0,0 +1,4 @@
+---
+---
+
+docs: add doc section for `UTXO` model

apps/docs/.vitepress/config.ts

@@ -70,6 +70,12 @@ export default defineConfig({
               },
             ],
           },
+          {
+            text: 'The UTXO Model',
+            link: '/guide/the-utxo-model/',
+            collapsed: false,
+            items: [],
+          },
           {
             text: 'Creating a Fuel dApp',
             link: '/guide/creating-a-fuel-dapp/',

apps/docs/src/guide/the-utxo-model/index.md

@@ -0,0 +1,34 @@
+# The UTXO Model
+
+In UTXO (Unspent Transaction Output) based systems, each coin is unique, similar to how physical currency bills have different denominations.
+
+A UTXO represents a coin with a specific amount, similar to having a $10 or $5 bill. It's crucial to understand this unique feature of UTXOs, as it differs significantly from Ethereum's account-based system.
+
+In Ethereum, balances are tracked as cumulative totals, similar to a bank account, rather than as distinct 'coins' or 'bills'.
+
+## Why UTXOs Matter
+
+Each UTXO corresponds to a unique coin and has an associated amount. This model allows for greater transparency and control in cryptocurrency transactions. Understanding UTXOs is key for effectively managing and tracking your digital assets.
+
+## How UTXOs Work
+
+When you create a transaction, you will use UTXOs from your account to fund it. Here's a step-by-step explanation:
+
+`1. Selecting UTXOs`: The SDK selects one or more UTXOs from your account that together are equal to or greater than the transaction amount plus the transaction fee.
+
+`2. Spending UTXOs`: These selected UTXOs are used to fund the transaction and cover the transaction fee. For example, if you need to send $15 and the transaction fee is $1, and you have $10 and $6 UTXOs, both will be used.
+
+`3. New UTXOs`: If the total value of the selected UTXOs exceeds the transaction amount plus the transaction fee, the difference is returned to your account as new UTXOs. For instance, if you spend a $20 UTXO for a $15 transaction with a $1 fee, a new UTXO worth $4 will be created as change and added back to your account.
+
+In summary, the original UTXOs used in the transaction are marked as spent and cannot be used again. The new UTXOs are available for future transactions.
+
+Suppose you have the following UTXOs in your account:
+
+- $10 UTXO
+- $20 UTXO
+
+You want to send $15 to someone, and the transaction fee is $1. Here's what happens:
+
+- The $20 UTXO is selected to fund the $15 transaction and cover the $1 fee.
+- The transaction is completed and the $20 UTXO is spent.
+- A new $15 UTXO is generated to the recipient, and a new $4 UTXO (change) is created and added to your account.

apps/docs/src/guide/wallets/checking-balances.md

@@ -1,19 +1,5 @@
 # Checking balances
 
-## Understanding the UTXO Model
-
-In UTXO (Unspent Transaction Output) based systems, each coin is unique, similar to how physical currency bills have different denominations.
-
-A UTXO represents a coin with a specific amount, similar to having a $10 or $5 bill. It's crucial to understand this unique feature of UTXOs, as it differs significantly from Ethereum's account-based system.
-
-In Ethereum, balances are tracked as cumulative totals, similar to a bank account, rather than as distinct 'coins' or 'bills'.
-
-## Why UTXOs Matter
-
-Each UTXO corresponds to a unique coin and has an associated amount. This model allows for greater transparency and control in cryptocurrency transactions. Understanding UTXOs is key for effectively managing and tracking your digital assets.
-
-## Getting a Wallet's Balance
-
 To check the balance of a specific asset, you can use [`getBalance`](../../api/Account/Account.md#getbalance) method. This function aggregates the amounts of all unspent coins of the given asset in your wallet.
 
 <<< @/../../docs-snippets/src/guide/wallets/checking-balances.test.ts#checking-balances-1{ts:line-numbers}