Copyright is the law that protects someone's original work. This might mean artwork, writing, music, etc.
Plagiarism is the act of taking someone's original work and claiming as your own without giving any credit.
Fair Use is, as defined by Dictionary.com, "reasonable and limited use of copyrighted material so as not to infringe upon copyright."
Students and adult writers alike need to understand the importance of properly citing sources to avoid plagiarism and to respect copyright laws and intellectual property. Here are some resources to help with that: