A patent is the exclusive right to make, use or sell an invention in a country. This invention can be a product or a method of making a product, although since recently also methods of doing business and computer programs can be patentend. In order to get this right, the inventor must apply for a patent at his patent office. He must fully disclose how the invention works and how it can be constructed and applied. This allows (at least in theory) others to make use of the invention. In return for his disclosure, the inventor gets the exclusive rights for a limited time (typically 20 years after applying for the patent).
There are two important criteria that determine whether an invention can be patented:
When an inventor applies for a patent, the patent office searches the available literature to determine whether the invention is novel, and based on the most relevant publications they find, they determine whether it would be obvious to invent what is in the patent. If the invention is found to be both novel and non-obvious, the inventor gets the patent.
It is important to note that the tests for novelty and obviousness are done on the basis of the knowledge people had at the moment the patent was filed. As it may take several years for a patent application to be granted, the idea behind the invention may already have been published by someone else, but if that publication was done after the day the patent was filed, it does not count in determining the novelty.
When you invent something, but never publish or produce the idea, others can still file for a patent, and you may then be infringing when you later decide to produce the invention. In some countries, most notably the USA, there is the notion of the "true inventor", who first invented something. Others cannot patent the invention, if the "true inventor" can prove he invented it first. Other countries, such as most European countries, have a simple policy: whoever applies first, gets the patent.
It is possible to get a patent in more than one country. An inventor can apply for the patent in several countries at a time, or apply in one first, and within a year apply in others as well. There are several treaties that make this process easier. For example, as there is no "European patent" which is automatically valid in all European countries, an inventor would have to apply for a patent in all countries separately. To avoid this, he can apply at the central European Patent Office and process the application one time; if this is done successfully, the patent application can then be transformed into national patents without extra effort.
Patents are very expensive, as the idea is to make the whole process self-sufficient. It is only interesting to apply for a patent when the inventor expects to make a lot of money from his invention, either by selling the invention in a monopoly position, or by licensing other people to do so. Licensing can be a very lucrative business if your invention is very useful.
More information on patents, copyright, trademarks and other Internet-related law is available on Iusmentis.com.