The Online Android SDK Manager is a online tool that allows you to Download and update packages for the Android SDK.
The sdkmanager tool is provided in the Android SDK Tools package (25.2.3 and higher) and is located in android_sdk/tools/bin/.
Once downloaded, you can extract the downloaded zip file in the appropriate directory indicated inside as the Android SDK Location.
Tools are useful for building, managing and controlling Android apps.
Includes essential tools such as ProGuard.
Includes tools to build Android apps.
Includes various tools required by the Android platform, including the adb tool.