Supergrain is an open source platform that allows businesses to integrate their applications with various SaaS tools easily. It provides developer tools and APIs for bi-directional data synchronization, enabling data to flow between applications and SaaS platforms. The platform is scalable and includes features like managed authentication and a common schema, which streamline the integration process. Supergrain aims to help B2B SaaS companies quickly create and maintain product integrations while ensuring security and compliance.