As it was mentioned, renBTC is an ERC-20 token built on Ethereum, which is pegged to Bitcoin. It means that it is always possible to redeem renBTC for one Bitcoin. It aims to retain its value at close to the Bitcoin market rate.
RenBTC is a competitor to Wrapped Bitcoin (wBTC). Its main difference is the usage of a decentralized network of nodes, which is called Darknodes. So, the users are able to burn and mint the tokens without completing KYC. Moreover, the private keys of RenVM (ECDSA) are completely private, so it creates decentralized and permissionless Bitcoin tokens on the Ethereum blockchain.
With renBTC it is quite easy to mint the token - users should send their BTC to RenVM, which mints renBTC tokens on the Ethereum blockchain.
RenBTC is not a synthetic token. On the contrary, it’s a direct supply peg, which has enough BTC in their reserves to fulfill the circulating renBTC tokens.
To redeem renBTC, the user should send their renBTC back to RenVM, where the native Bitcoins will be released and sent to the user’s address.