The term "copyright" refers to a variety of rights that exist for literary, musical, stage or artistic works and for sound recordings, films, broadcasts and other creative work. Under the copyright laws, these rights are exclusive to the copyright holder and enable the copyright owner to dispose of his / her works and prevent unauthorized use.
Originally, the copyright laws allowed the author of a work to protect this work from duplication. Gradually, however, the copyright laws have been extended and allow copyright owners to prevent or dispose of other things, such as the processing or public performance of the copyrighted work, inclusion of the work in a broadcast or distribution of the work in material form, the Internet. Since such rights are the exclusive property of the copyright owner, anyone who wishes to do so will first need permission from the copyright owner.
Copyright may be for various things - for example, music, lyrics, photographs, works of art, books, speeches, TV broadcasts and films. Even if it appears to be the work of an individual, several copyrights of different owners may exist. For example the artist, the gallerist who exhibits the work, the photographer who captured the artwork etc.
The sharing via the internet, requires the permission of all of these copyright holders either directly or through their representatives (for example through a collecting society).