Copyright is about ownership, eg: of a literary, dramatic, musical or artistic work, such as a book, play, song or painting. In theory, some things cannot be copyrighted, such as a surgical operation or a way of doing business.
Initially, the author of a work is the copyright owner, but ownership can be sold or transferred to someone else. Copyright on books, etc. normally lasts for seventy years after the death of the author. Sound recordings are usually protected for fifty years. However, this is not always the case.
The Internet has created massive opportunities for the infringement of copyright. The Internet provides text and illustrations in electronic format, making it easy for the unscrupulous user to cut and paste material into their own documents. Trying to pass someone else’s work off as your own is known as plagiarism.
The same rules generally apply to materials published on the Internet as to those published on other media. Almost everything on the Internet is copyright, so when you download material you should ensure that you are not breaking copyright law.
The greatest areas of commercial concern have been copyright infringements involving music files and still and moving images, particularly movies and TV programmes. A digital file can be cheaply and easily copied and distributed anywhere in the World via the Internet. The creator of the original work is excluded from the process and thus receives no financial
You can also find more information at: Copyright Crash Course