Plagiarism is defined as literary theft, where one steals the writing of someone else and publishes it as their own. It can be on a student level, where students steal or copy someone else’s assignments. It can be on article writing; one writer steals someone else’s words and submits it as their own. It can even be at research level, where one researcher copies another’s work and publishes it as their own work.
In some countries and cultures copying and publishing is not considered to be a crime. There it is believed that any work becomes public information once it is published and can be freely used by others. However in the United States and in some other Western countries plagiarism is considered a very serious offense. A student can get expelled, a writer, researcher can lose their jobs and even face imprisonment.
Plagiarism is a violation of the honor code, and it is a federal crime which violates copyright laws. Copyright laws strive to balance the interest of users and copyright owners. Copyright owners have exclusive rights and control to prohibit users from using someone’s work in a specific way without the owner permission. A copyright owner has exclusive rights to control publication of his work, distribution of his work, public display of his work, adaptation of his work and reproduction of his work.
Only that material can be plagiarized which is not protected by copyright laws. Documents like: standard/common works like calendar, logical and unoriginal reprints of public domain works, freeware software available without any restriction, facts, ideas and processes and phone books.
You should always do your own original work and avoid plagiarism at all costs. If you do need to quote you must give credit to the originator of the quote and document it properly. Paraphrasing is another form of plagiarism that must be avoided.