The Android SDK (Software Development Kit) is a collection of tools and libraries that developers use to create applications for the Android operating system. It includes essential components like a code editor, debugging tools, and emulators that allow developers to test their apps on virtual devices. By using the Android SDK, developers can access various features of the Android platform, such as user interface elements, data storage, and device sensors. This toolkit simplifies the app development process, making it easier to build, test, and deploy applications on a wide range of Android devices.