Definition:
Copyright refers to laws that relates to the use of the work of a designer, artist or author. This includes copying, distributing, altering and displaying creative, literary and other types of work. Unless otherwise stated in a contract such a referencing , the author or designer of a work retains the copyright.
It is basically granting exclusive rights to publish and sell literary or musical or artistic work.

"Copyright law originated in the United Kingdom from a concept of common law; the Statue of Anne 1709. It became statutory with the passing of the Copyright Act 1911. The current act is the Copyright, Designs and Patents Act 1988."

The creative commons (CC) website allows users to share their creativity with each other. People can find, use, remix and edit creative work from anywhere around the world and not get prosecuted by copyright laws. The Creative commons was founded by Lawrence Lessig. So when someone uploads something on the internet they go to the CC website and choose a license. Once they have chosen their license they are given a HTML to apply to the site that their work is on.

One of the most common illegal copyright systems is downloading music or films from the internet.
Copyright protects those who author or produce creative works, whether through movies, TV shows, music, software, books or games. Copyright protection of films and television helps preserve the jobs of 2.4 million Americans who work as actors, writers, set painters, electricians, carpenters and so many others who contribute to make movie magic.

Trademarks are words, names, designs or logos used to identify the source of a product. Trademarks can last as long as they are used for that purpose. Copyright, on the other hand, gives the creators of original works certain exclusive rights to license, sell, reproduce, publicly perform and otherwise exploit the work, usually for a limited time.

http://www.mpaa.org/contentprotection/faq

Copyleft is a way of guaranteeing digital freedoms. When programs, software and other work is made totally free without any copywriting at all it is at risk of being modified and redistributed as a proprietary product.

Copyleft says that anyone who changes or modifies programs and software must pass on all the same rights and privilages of freedom to all later users.

To copyleft a program, we first state that it is copyrighted; then we add distribution terms, which are a legal instrument that gives everyone the rights to use, modify, and redistribute the program's code, or any program derived from it, but only if the distribution terms are unchanged. Thus, the code and the freedoms become legally inseparable.

Proprietary software developers use copyright to take away the users' freedom; Copyleft, use copyright to guarantee their freedom. That's why we reverse the name, changing “copyright” into “copyleft.”