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.
As such, many decentralized systems use WETH as the base asset; to give traders the choice of which asset to trade with, AirSwap uses both ETH and WETH as base assets. Unwrapping and wrapping ETH and WETH make it so it’s easy for traders to go between the two.