BaaS is a model for providing app developers with backend cloud storage and APIs while also providing features like user management, push notifications, and social integration. Parse is a popular BaaS platform that allows developers to store and query data, implement user authentication and authorization, and send push notifications, all through a simple open source SDK. The Parse SDK allows saving, retrieving, updating, and deleting objects from the cloud and includes support for features like files, users, queries, and local data storage.