A: According to the Copyright office at the Library of Congress, copyright infringement "occurs when a copyrighted work is reproduced, distributed, performed, publicly displayed, or made into a derivative work without the permission of the copyright owner." (http://www.copyright.gov/help/faq/faq-definitions.html)
While the term "theft" is not strictly applied to the act of infringing the rights of a copyright owner, "piracy" has been applied to copyright infringement since the Renaissance. Piracy traditionally refers to any act violating the intellectual property rights of a copyright owner with the goal of financial gain. More recently, the definition of this term has been broadened to include any unsanctioned copying for any motivation, financial or not. (http://arstechnica.com/tech-policy/news/2012/04/raskally-fellows-are-copyright-infringers-pirates-and-thieves.ars/1)
A: Sometimes the easiest way to use copyrighted materials legally is to ask the permission of the copyright owner, who may be the creator of the work, a publisher, or some other entity. Sometimes an industry licensing body acts on behalf of copyright owners to grant permissions. Look for the copyright symbol (C) at the beginning or end of a printed work, or on the title screen of a media production for information about the copyright owner. Note that sometimes the copyright owner will ask for a fee for the use of the material, so you have to decide if the benefit of acquiring the legal right to copy the work is worth the cost in money and time to get the authorization. The Columbia University Libraries page on obtaining copyright permissions is an excellent resource for more information about obtaining permissions, including sample permission letters.
A: Peer-to-peer file sharing is a process by which people use technology to share files (such as audio, video, or software) between individual computers. (http://www.ftc.gov/reports/p2p05/050623p2prpt.pdf)
A: The law does not prescribe many clear rules for copyright compliance--just guidelines. Organizations have put together guidelines that you can follow and which, if followed, will keep you within the law. Such guidelines are called "bright line" policies. You can see examples of these guidelines here. You can also see the Common Situations Examples page here. You can also look in the Copyright Advisory Network Forum if you think your question may have been asked/answered by others.