It is a decentralized application where users first need to whitelist themselves, After whitelisting users can able to participate in presales of NFT, the presale button is only visible if the owner of the contract is connected to the website only the owner can start the presale which complete in 10 minutes. If the user is not whitelisted then the user needs to publicly mint NFT. After completion of minting NFT, if the user has an NFT ERC721 token then the user will get 10 Gang ERC20 tokens free of cost, else user needs to pay for tokens thus in both case user need to pay gas fees.