What are Android Support Libraries & Differnces

Android Support Libraries
 What are these??
    For Supporting  the old versions with new code. in layman it like new versions are giving their functionality  to old versions.

It will help coders to create code with new functionality  (that is not present in old versions) for devices with older versions as well.

 There are 3 main support versions for android libraries - V4, V7 ,V13
So you can say these libraries are there to help backward compatible.
Version 7 isn't used that much and was specifically for Grid Layout

Version4	Version 7	Version 13
This library is designed to be used with Android 1.6 (API level 4) and higher.	There are several libraries designed to be used with Android 2.1 (API level 7) and higher	This library is designed to be used for Android 3.2 (API level 13) and higher
The main features here are backwards-compatible versions of FragmentManager and LoaderManager. click here for more info	This library adds support for the Action Bar user interface design pattern.	Classes  FragmentPagerAdapter    FragmentTabHost FragmentStatePagerAdapter    FragmentCompat
This library is designed to be used with Android 1.6 (API level 4) and higher.	his library is located in the <sdk>/extras/android/support/v7/appcompat/	This library is located in the <sdk>/extras/android/support/v13/
follow the instructions for adding libraries without resources.	instructions for adding libraries with resources.	To include it in your application project, follow the instructions for adding libraries without resources.

How to download Suppot libraies??
Right clicl your project in eclipse >select Android Tools> then click Add Compatibility Library.
then-

 Other way to download
Eclipse -> Window -> Android SDK and AVD Manager -> Available Packages -> Download the compatibility library v4.

 Adding to project:

• Project Menu > Properties > Java Build Path > libraries tab >Add external Jars
• Done.