When we create an Android project , It comes with several sub-directories. Android project has also its directory structure which may different in different version of Eclipse. Structure which we explained are on Eclipse Mars.
Above is the structural view of any Android project in Eclipse. I'll explain each one by one.
1)src : src is a folder where main source code of your project exists. All your packages and class files reside in this folder.
2) gen : gen is a folder where R.java file resides. All the resources in your project like images, strings, sounds, videos you can access in your source code or java file using R.java.
3)Android 6.0 : This folder hold the jar file of the target android version.This files have the classes of that version file which is useful for developers.
4)assets: The directory that holds other static files that you want packaged with the application for deployment onto the device
5)bin: The directory that holds the application once it is compiled.
6)libs : libs/: This directory that holds third-party JARs your application requires.
7)res : This folder includes the resources like strings , images , audio , video , animation files etc.
8)drawable : This folder holds the images that we are going to use into our application.Bitmap files (.png, .9.png, .jpg, .gif) or XML files that are compiled into Bitmap files ,Nine-Patches (re-sizable bitmaps) ,State lists ,Shapes ,Animation drawables ,Other drawables.
9)layout : This folder holds all XML file for your all activities. There are individual XML file for each activity. You can drag and drop controls on the layout, change properties of controls. Ultimately this is your design hub for your Android project.You can design an custom view which you are going to use in you projects termed as custom layouts.
10)menu: This folder used to define menu resource items using XML. We can also do the same using java codes but better to use XML file in android.
11)values : It holds the files like string.xml , dimen.xml , color.xml , style.xml. where string.xml hold string type resources , dimen.xml holds dimension values.
12) AndroidManifest.xml : This file holds the complete information about the project . In this file we need to register about the components which we are using into the application like Activity , Service , Receivers etc.