A patent, literally speaking, is a document, issued by a government, granting certain rights to someone who has invented something. These rights are sort of like property rights: They confer ownership onto the person the patent is granted. The most significant right that the patent offers is a sort of monopoly: In exchange for explaining your invention to the community at large, you are granted a right to be the only person to be able to manufacture or directly profit from that invention for a certain length of time -- usually 20 years or so.
How Do You Get a Patent?
Well, the first thing you've got to do is invent something. That something has to be categorized as an invention, defined loosely as any "art, process, machine, manufacture, or composition of matter" or an improvement on an existing invention. This invention also has to be new, nonobvious, and useful.
For something to be new, no one could have made it before. Although that sounds nice and simple, it's actually quite difficult to determine: What if someone can show they made it, but they haven't distributed it to the public? What if someone made it in some other country? What if someone made something that's close to the same thing, but isn't really? Novelty is one of the hardest parts of a patent to both defend and prove at the time of application.
To get a patent for something, it's not enough that it's new, it's also got to be nonobvious: That is, theoretically, your invention can't be something that someone who knew everything that had been published in the field, but with no imagination, could figure out and make. The problem with nonobviousness is that it's determined after you've shown your invention to someone: A whole lot of people could say "yeah, I coulda done that" after they've seen something done (think of the vacuum cleaner, or the first screw-top beer bottle). So nonobviousness is harder to show than you might think.
To be patentable, an invention must be directed toward a specific use. It really doesn't matter if it's beneficial to the public, as long as it's theoretically useful for something. But it's not enough to show that you've invented something new: It's got to have a purpose of some kind.
Getting a Patent
Once you've shown that your invention is novel, nonobvious, and useful, you've got to apply to the government patent office in the country in which you want the patent rights in (that is, the country in which you want to sell or profit from your invention). You can apply to more than one country, but each application costs more money.
An invention is different from a discovery, and a scientific discovery is not patentable. That is, you can't patent lightning, or the theory of relativity, or anything that already exists in nature. This rule gets a bit muddled up when you start dealing with DNA sequences, and the like, and both the patent office and the courts are having a lot of problems with this at the moment.
In many countries, you also can't patent life-forms, though you can patent the process you took to make or modify that life-form. For example, in Canada, the Harvard Mouse (the famous p53-transgenic mouse that is highly susceptible to cancer) was not granted a patent; however, the process they undertook to make the mouse could be patentable if no one had done it before).
Rights Granted Under Patent
Generally speaking, you are granted two exclusive rights when you're given a patent for something: Barring certain exemptions, like some research and educational use, a patent gives the holder the exclusive right to use and sell his or her invention.
Right to Use
Theoretically, you're the only person that's allowed to use your patented invention, unless you sell either the invention or the right-to-use to someone else.
Right to Sell
You can sell your patent, and all the rights contained within it, to whoever you want (e.g., sell the patent and therefore the invention known as the vacuum cleaner). You also have the exclusive right to sell your invention to whoever you want (e.g., sell vacuum cleaners). By exclusive, this means that no one (including foreign companies) can sell vacuum cleaners in the country you have the patent in, for the duration of the patent.
Well, that's about a brief introduction to patents as you can get! In the following couple of articles, we'll be dealing with some of the more common problems with patents.