Definition. Wrapped BTC (WBTC) Balance is the amount of BTC (USD) held by BitGo as backing for Wrapped Bitcoin (WBTC), the first ERC20 token backed 1:1 with Bitcoin and designed to represent Bitcoin on the Ethereum blockchain.

Technical. BitGo is the custodian responsible for minting new WBTC ERC20 tokens and guaranteeing that newly minted tokens are backed by actual BTC.