Daily.co provides a video calling API that allows developers to add video calls to their mobile apps without requiring users to download anything or integrate a new library into the app. The API supports various platforms, including Chrome on Android and Safari on iOS, desktop browsers, and Electron applications. To get started with Daily.co, developers can use web offerings or leverage native mobile libraries when they become available. The API also provides features like room creation, meeting tokens, and customizable user interfaces. Developers can test the API using a daily-js front-end library and integrate it into their apps using WebViews on Android or SFSafariViewController on iOS. Additionally, Daily.co offers resources for developers, including REST API reference docs, a 5-minute tutorial, and in-depth guides on creating and managing video call rooms.