Default resources are items that are not specific to any particular device or form factor, and therefore are the default choice by the Android OS if no more specific resources can be found. As such, they're the most common type of resource to create. They're organized into sub-directories of the Resources directory according to their resource type:
In the image above, the project has default values for drawable resources, layouts, and values (XML files that contain simple values).
A complete list of resource types is provided below:
animator – XML files that describe property animations. Property animations were introduced in API level 11 (Android 3.0) and provides for the animation of properties on an object. Property animations are a more flexible and powerful way to describe animations on any type of object.
anim – XML files that describe tween animations. Tween animations are a series of animation instructions to perform transformations on the contents of a View object, or example, rotation an image or growing the size of text. Tween animations are limited to only View objects.
color – XML files that describe a state list of colors. To understand color state lists, consider a UI widget such as a Button. It may have different states such as pressed or disabled, and the button may change color with each change in state. The list is expressed in a state list.
drawable – Drawable resources are a general concept for graphics that can be compiled into the application and then accessed by API calls or referenced by other XML resources. Some examples of drawables are bitmap files (.png, .gif, .jpg), special resizable bitmaps known as Nine-Patches, state lists, generic shapes defined in XML, etc.
layout – XML files that describe a user interface layout, such as an activity or a row in a list.
raw – Arbitrary files that are saved in their raw, binary form. These files are compiled into an Android application in a binary format.
values – XML files that contain simple values. An XML file in the values directory does not define a single resource, but instead can define multiple resources. For example one XML file may hold a list of string values, while another XML file may hold a list of color values.
xml – XML files that are similar in function to the .NET configuration files. These are arbitrary XML that can be read at run time by the application.