The Library Panel is utilized to store objects that can be reused throughout the movie. Items stored in the library are considered a Symbol. The Library helps Flash keep file size down by storing the basic information about objects in one place. When these objects are reused, known as an instance, Flash does not need to store the basics again. It only stores what is different about the new instance of the object. Certain properties of the instance can be changed, for example, transparency, color, size, and rotation.
Below, notice the Library is open on the right and has one Graphic Symbol, called Logo.