Contracts can be deployed directly to RenVM. The inputs, outputs, and states of these contracts are kept secret from everyone, including the Darknodes that power RenVM. Check out the specification on GitHub for more information about how RenVM works.
People can communicate with these contracts by sending (and receiving) secret messages. Only the sender of the message knows its contents. This allows developers to build all kinds of applications that are trust-less, permission-less, and respect the privacy of sensitive data. This is particularly useful when building privacy-centric applications (e.g. dark pools), or applications that handle sensitive information (e.g. personal financial applications).
DeFi Sensitive information is often needed when building DeFi applications, such as information about individuals' wealth. By deploying DeFi applications directly to RenVM, this information can be kept secret.
Dark pools Dark pools are a type of exchange where the order book is hidden. Running a dark pool on RenVM means that no third party needs to be trusted to keep the order book hidden, or to ensure the integrity of the order matching engine.
Zero-Knowledge Interoperability ZCash and other privacy coins can be interoperated between blockchains without compromising privacy.