Android official documentation: (3) resources-3.6.1 Resource Type Overview

Each of the documents in this section describe the usage, format and syntax for a certain typeof application resource that you can provide in your resources directory (res/).

Here's a brief summary of each resource type:

Animation Resources

Define pre-determined animations.
Tween animations are saved in res/anim/And accessed from R.animClass.
Frame animations are saved in res/drawable/And accessed from R.drawableClass.

Color State List Resource

Define a color resources that changes based on the View state.
Saved in res/color/And accessed from R.colorClass.

Drawable Resources

Define various graphics with bitmaps or XML.
Saved in res/drawable/And accessed from R.drawableClass.

Layout Resource

Define the layout for your application UI.
Saved in res/layout/And accessed from R.layoutClass.

Menu Resource

Define the contents of your application menus.
Saved in res/menu/And accessed from R.menuClass.

String Resources

Define strings, string arrays, and plurals (and include string formatting and styling ).
Saved in res/values/And accessed from R.string, R.array, And R.pluralsClasses.

Style Resource

Define the look and format for UI elements.
Saved in res/values/And accessed from R.styleClass.

More Resource Types

Define values such as booleans, integers, dimensions, colors, and other arrays.
Saved in res/values/But each accessed from unique RSub-classes (such R.bool, R.integer, R.dimen, Etc .).