Android SDK Manager is a tool that helps you install and update the tools for developing Android applications. It displays a list of available packages, which you can install or update to make your development environment up-to-date. When you want to update a package, you can click on the update dash to do so. This command line tool can also be used to install SDK tools. The sdkmanager command-line tool can be used to download the tools for Android applications.
The sdkmanager can perform the following tasks. You can select packages from different channels by using the channel option. If you want to install packages from only one channel, select -channel=canary. Similarly, -channel=0 will list only stable packages. If you want to install packages from more than one channel, make sure you wrap their paths in quotes. Once the packages are installed, you can go ahead and create your app.
Once you have installed the SDK on your computer, the SDK Manager will display the list of installed packages. The list includes the Android Platforms, sample applications, and AVD system image. You can also view the extra packages you need to download. Those extra packages are called build-tools and SDK tools, and will have to be downloaded from the internet. It will take you to a page in the SDK Manager that lists the tools you need.