difference between VRFCoordinatorV2Interface and VRFConsumerBaseV2

[TimeKeyRoll]

What's the difference between -
"@chainlink/contracts/src/v0.8/interfaces/VRFCoordinatorV2Interface.sol";
And
"@chainlink/contracts/src/v0.8/VRFConsumerBaseV2.sol";

So one of this is contract and other is interface. What they do do and what's the difference in them?
P.S please try not to use technical language.Thanks in Advance.

[adityabhattad2021]

First about VFRConsumerBaseV2:
In order to use VRFCoordinator our contract as the consuming contract must inherit (i.e. contract Lottery is VRFConsumerBaseV2 {}) VRFConsumerBaseV2 and implement the fulfillRandomWords function inside our consumer contract itself,

function fulfillRandomWords(
		uint256, /*requestId*/
		uint256[] memory randomWords
	) internal override {
		uint256 indexOfWinner = randomWords[0] % s_players.length;
		address payable recentWinner = s_players[indexOfWinner];
		s_recentWinner = recentWinner;
		(bool success, ) = recentWinner.call{value: address(this).balance}("");

		if (!success) {
			revert Lottery__TransferFailed();
		}

		emit WinnerPicked(recentWinner);
		s_lotteryState=LotteryState.OPEN;
		s_players = new address payable[](0);
		s_lastTimeStamp=block.timestamp;
	}

which is the callback VRF function. Submit your VRF request by calling requestRandomWords of the VRF Coordinator like we did in our lottery contract:

function performUpkeep(bytes calldata  /* performData */) 
		external
		override 
	{

		(bool upkeepNeeded, ) = checkUpkeep("");
		if(!upkeepNeeded){
			revert Lottery__UpkeepNotNeeded(
				address(this).balance,
				s_players.length,
				uint256(s_lotteryState),
				((block.timestamp - s_lastTimeStamp) > i_interval),
				upkeepNeeded
			);
		}

		s_lotteryState=LotteryState.CALCULATING;


		// Request the random number.

		// This will return request id
		s_requestId = i_vrfCoordinator.requestRandomWords(
			i_gasLane,
			i_subscriptionId,
			REQUEST_CONFIRMATIONS,
			i_callBackGasLimit,
			NUM_WORDS
		);

		// This line is redundant as VRFCoordinator is already emitting the requestId
		emit RequestedLotteryWinner(s_requestId);
	}

then VRF coordinator emits an event.
The event is picked up by the VRF node and will wait for the specified number of block confirmations to respond back to the VRF coordinator with the random values and a proof (requestConfirmations).

The VRF coordinator verifies the proof on-chain then calls back the consuming contract fulfillRandomWords function.

and now VRFCoordinatorV2Interface:
It is the interface of VFRCoordinator itself. We use interface in our contract as we need to call VRFcoordinator's requestRandomWords function (refer the above code in performUpKeep function), to use its function inside our contract we need to know what are the functions in VRFCoordinator and what are its parameters which are needed to be passed inside it, which are provide by its interface as we save i_vrfCoordinator as the type VRFCoordinatorV2Interface with this line which tells our contract that i_vrfCoordinator is VRFCoordinator and has the function specified in VRFCoordinatorV2Interface.

VRFCoordinatorV2Interface private immutable i_vrfCoordinator;

(to know more about interface refer #2132)

[TimeKeyRoll]

Where does interface folder resides!?

[othaime-en]

In the same folder you found VRFConsumerBaseV2. @chainlink/contracts/src/v0.8/
The full path is will be @chainlink/contracts/src/v0.8/interfaces/VRFCoordinatorV2Interface.sol

[TimeKeyRoll]

Ser that's what I have been trying doing as well. But it's not there.
If incase you have a screenshot that would help me a ton. :)

[adityabhattad2021]

In your lottery contract these should be your import files.

Right click on this line import "@chainlink/contracts/src/v0.8/interfaces/VRFCoordinatorV2Interface.sol"; > click on go to definition.

[TimeKeyRoll]

Best and easy way. Appreciated man. Thanks a bunch.