Put plainly, WETh is “Wrapped ETH” or “Wrapped Ethereum”. In the beginning there was just Ether token. Ether or ETH is the native currency that is built on Ethereum blockchain. Then there was “Alt tokens”. When a dApp (decentralized app) is built off of the Ethereum blockchain it usually implements its own form of Token. Think of Aave (AAVE), Chainlink (LINK), Maker (MKR), Wrapped BTC, Matic (MATIC) or even ApeCoin (APE).
Finally the ERC-20 Standard developed after the release of ETH that defines how tokens are transferred and how to keep a consistent record of those transfers among tokens in the Ethereum Network.
Why do you need ETH
ETH doesn’t conform to it’s own ERC-20 Standard. ETH was the proto-token of the EThereum Alt tokens, which means it was built before the ERC-20 standard existed.
Wrapping ETH allows you to trade directly with ALT tokens. The reason you need wETH is to be able to ETH for other ERC-20 standard tokens on decentralized platforms like uniswap. Because decentralized platforms running on Ethereum use smart contracts to facilitate trades directly between users, every user needs to have the same standard format for every token they trade.
