Copyright is an unregistered right and protects the form of expression of ideas (not the ideas themselves) – examples include literary, musical, dramatic and artistic works.
In summary it prevents others from copying your work – it does not prevent someone from creating the same work independently.
For copyright to subsist, the work must be:
i) original i.e. the work must not have been copied
ii) created using sufficient skill and labour
iii) represent the authors own intellectual creation
Duration of copyright varies depending on the work but generally speaking lasts for the life of the author plus 70 years from the end of the calendar year in which the author dies.