Drawable is a virtual resource that may be utilized as a background, a title, or anywhere else on the screen. It’s turned into a subclass of android.graphics.drawable. A drawable resource is a generic term for a drawing-friendly image. A graphics file (bitmap) is the most basic example, which is represented in Android by the BitmapDrawable class.
Drawable is kept in one of the res/drawable directories as a separate file. By default, the ADT project creation process generates these directories. Bitmaps for various resolutions would be stored in the res/drawable subfolders -mdpi, -hdpi, -xhdpi, and -xxhdpi. If these bitmaps are given in a separate folder, the Android system will automatically choose the proper one based on the device setup.