The majority of intellectual property rights provide creators of original works economic incentive to develop and share ideas through a form of temporary monopoly.
Although many of the legal principles governing intellectual property have evolved over centuries, it was not until the late 20th century that the term intellectual property began to be used as a unifying concept.
source:http://en.wikipedia.org/wiki/intellectual property
Intellectual property rights:
Intellectual property rights are considered by economists to be a form of temporary monopoly enforced by the state (or enforced using the legal mechanisms for redress supported by the state).
Intellectual property rights are usually limited to non-rival goods, that is, goods which can be used or enjoyed by many people simultaneously—the use by one person does not exclude use by another. This is compared to rival goods, such as clothing, which may only be used by one person at a time. For example, any number of people may make use of a mathematical formula simultaneously. Some objections to the term intellectual property are based on the argument that property can only properly be applied to rival goods (or that one cannot "own" property of this sort).