In order to balance the needs of users with those of rightsholders and to preserve copyright's purpose to promote science and the useful arts, copyright law contains a number of exceptions.
Many of the exceptions in copyright law apply only to certain types of works under very specific conditions. The exceptions can be difficult to understand and apply without the advice of a lawyer.
In contrast, fair use is easier to understand, applies to all types of works, and is flexible. It is for these reasons that this guide recommends relying on fair use when deciding when and how to use (or not to use) third-party copyrighted material in online education.