What is library?
All the images added to Eagle will be placed in the "LIbrary". The library is the main way for Eagle to store images. You can think of the library as an album, we can store different types of images in the corresponding album. Different from the computer folder, the library is independent of each other and has own folders, tags, images.
For example, the images in the "Graphic Design" library won't be affected by the "Architectual Design"