Feature: Added section explaining inter contract calls

docs/quick-start/developers/lottery-game-smart-contract/index.md

@@ -1380,6 +1380,41 @@ Enter the required param <symbol>: ELF
 Enter the required param <owner>: $WALLET_ADDRESS
 ```
 
+## Understanding Inter-Contract Calls in aelf
+
+In this section, we'll explore how inter-contract calls work in the aelf blockchain using the lottery game example from the tutorial. This will help you understand how different smart contracts can interact to perform complex operations.
+
+### 1. **Smart Contract Overview**
+   - **Lottery Contract**: Manages the game, including buying tickets, drawing winners, and distributing prizes.
+   - **Token Contract**: Handles the token transactions needed for buying lottery tickets.
+
+### 2. **Ticket Purchase Process**
+   - **Initiating Purchase**: When a user wants to buy a lottery ticket, they interact with the Lottery Contract.
+   - **Token Transfer Requirement**: The Lottery Contract must verify that the user has enough tokens and transfer those tokens to the lottery’s account to complete the purchase.
+
+### 3. **Making an Inter-Contract Call**
+   - **Calling Token Contract**: The Lottery Contract needs to interact with the Token Contract to transfer tokens. 
+     - **Method Invocation**: It calls a method in the Token Contract, such as `Transfer`.
+     - **Parameters**: The call includes details like the sender’s address, the recipient’s address (the lottery account), and the amount of tokens.
+   - **Encoding and Sending**: The parameters are encoded into a transaction format and sent to the Token Contract.
+
+### 4. **Processing in the Token Contract**
+   - **Token Transfer**: The Token Contract processes the transfer request by deducting tokens from the user’s account and adding them to the lottery account.
+   - **Return Response**: The Token Contract then returns a result indicating whether the transfer was successful or if it failed.
+
+### 5. **Handling the Response**
+   - **Lottery Contract’s Role**: Once the Lottery Contract receives the response from the Token Contract, it checks if the transfer was successful.
+   - **Next Steps**: If successful, the Lottery Contract updates the user's lottery ticket entries and continues with the game logic.
+
+#### 6. **Authorization and Security**
+   - **Permission Checks**: Ensures that the Lottery Contract is authorized to invoke methods in the Token Contract.
+   - **Secure Transactions**: Ensures that token transfers are secure and correctly authorized.
+
+### 7. **Error Handling**
+   - **Failure Management**: If the token transfer fails (e.g., due to insufficient funds), the Lottery Contract handles the error by potentially reverting the transaction or notifying the user.
+
+By following these steps, you can see how inter-contract calls in aelf allow different contracts to work together smoothly. This modular approach helps in building complex applications like a lottery game by ensuring secure and authorized interactions between contracts.
+
 
 ## 🎯 Conclusion