Copyright laws protect the intellectual property rights of those who create new expressions of ideas, music, images (still & moving) websites, videogames, performances, architecture, software etc. It also protects the First Amendment of freedom of speech and right of the press.
The Fair Use Doctrine is an exemption from copyright laws which gives people the right to use copyrighted materials without permission or payment for limited purposes such as teaching, scholarship, research, criticism, comment and news reporting.
Public Domain refers to work that is not restricted by copyright and may be used freely without permission or payment.
Attribution: The act of attributing especially the act of establishing a particular person as the creator of a work of art.
Infringement: the action of breaking the terms of a law, agreement, etc.; violation.
TASL: when you are creating an attribution, remember this acronym.
Copyright Catechism II by 