Cartesi is a project that creates an operating system for decentralised applications by allowing complicated computations to occur away from the blockchain and in a Linux ecosystem. It makes the creation of DApps much easier, scalable and convenient for developers while also allowing those DApps to be more powerful and portable.
Using the Cartesi Side Chain, developers are also able to store their data (for a limited amount of time). This side chain is governed by a consensus algorithm and removes the need to relay with the layer-1 blockchain.