(At present, the development tool used for Android development is Eclipse. In the Eclipse compiled IDE environment, ADT is installed to provide the upgrade of development tools for Android development, which may be changed. It is simply understood as the upgrade and download tool of development tools under Eclipse. SDK (Software Development Kit): generally, it is a collection of development tools used by software engineers to build software for specific software packages, software frameworks, hardware platforms, operating systems, etc. In Android, it provides developers with library files and other tools for development. Simply understood as a collection of development toolkits, it is a toolkit used in the overall development. If you don't need Eclipse as your development tool, you don't need to download ADT, just download SDK to develop.
features\com.android.ide.eclipse.adt_ 10.0.0.v201102162101-104271.jar
features\com.android.ide.eclipse.ddms_ 10.0.0.v201102162101-104271.jar
features\com.android.ide.eclipse.hierarchyviewer_ 10.0.0.v201102162101-104271.jar
features\com.android.ide.eclipse.traceview_ 10.0.0.v201102162101-104271.jar
plugins\com.android.ide.eclipse.adt_ 10.0.0.v201102162101-104271.jar
plugins\com.android.ide.eclipse.ddms_ 10.0.0.v201102162101-104271.jar
plugins\com.android.ide.eclipse.hierarchyviewer_ 10.0.0.v201102162101-104271.jar
plugins\com.android.ide.eclipse.traceview_ 10.0.0.v201102162101-104271.jar
web\site.css
web\site.xsl
index.html
site.xml
.....)