Wrapped ETH or WETH is an ERC20 token that enables the trading of ETH for other ERC20 tokens on decentralized platforms. ETH was the proto-token of the Ethereum Alt tokens, which means it was built before the ERC20 standard exist. Subsequently, an ERC20 compliant wrapped ETH token was created to represent ETH 1:1 via smart contracts.
When you sell tokens on AirSwap, you will receive WETH in return. If you want to convert to ETH, simply go to the wallet within Instant and convert directly.