MongoDB Stitch` is a serverless platform that enables developers to build modern, cross-platform apps on top of `MongoDB`, covering various aspects such as application hosting, database interaction, and integrating with third-party services. The platform provides an easy-to-use interface for creating applications, hosting them online, and implementing authentication and authorization mechanisms. Through a series of videos and tutorials, users can learn how to build a basic blogging application using `MongoDB Stitch`, leveraging features like `QueryAnywhere` for commenting functionality, `Hosting` for deploying the app, and `Functions` and `Triggers` for automating tasks with minimal code. The platform also supports various authentication providers, making it easier for developers to focus on building their applications rather than implementing authentication logic.