The Cosmos SDK is an open-source framework designed for building blockchain applications. It allows developers to create custom blockchains that can interoperate with one another, promoting a more connected ecosystem. The SDK is built on the principles of modularity and flexibility, enabling users to choose the components they need for their specific use cases. One of the key features of the Cosmos SDK is its use of the Tendermint consensus algorithm, which ensures fast and secure transaction processing. This framework is part of the larger Cosmos Network, which aims to create an "Internet of Blockchains," allowing different blockchains to communicate and share data seamlessly.