Fonction SwapTokensAtAmount?

Smart Contracts
1

Hello,
Please someone can explain me this.

maxTransactionAmount = totalSupply * 4 / 100; // 4%
maxTransactionAmountTxn
maxWallet = totalSupply * 4 / 100; // 4% maxWallet
swapTokensAtAmount = totalSupply * 5 / 10000; // 0.05% swap wallet

What is swapTokensAtAmount please ?

Same for this :

// change the minimum amount of tokens to sell from fees
function updateSwapTokensAtAmount(uint256 newAmount) external onlyOwner returns (bool){
require(newAmount >= totalSupply() * 1 / 100000, "Swap amount cannot be lower than 0.001% total supply.");
require(newAmount <= totalSupply() * 4 / 100, "Swap amount cannot be higher than 4% total supply.");
swapTokensAtAmount = newAmount;
return true;

What is swap amount ?

Thanks you in advance.