In patent law, the term "invention" is defined loosely so that it can encompass a wide variety of objects. Obviously, if patents have to apply to things that don't exist yet, then the legal language must be fairly vague. In addition to standard technological machines and machine advancements, you can also patent certain computer programs, industrial processes and unique designs (such as tire or shoe-tread patterns). While none of the elements in these creations are new, the inventor may have combined them in a unique and innovative way. In the language of patent law, this constitutes an invention.
Some sorts of ideas are considered outside the realm of patents. No matter how innovative and beneficial they may be, certain notions are automatically public property the minute they are uncovered. The most prevalent examples of this are discoveries in the natural world. Scientists cannot patent laws of the universe, even though defining those laws may revolutionize a particular industry or change how we live. Einstein's Law of Relativity, for example, revolutionized the world of physics and will be forever linked with the man who devised it, but it has never been owned by anybody. This principle existed long before humans did, so, logically, it cannot be any person's intellectual property.
Scientists cannot patent a newly discovered plant or animal, either, though they may be able to patent a new plant or animal that was produced through genetic engineering. This is similar to the patenting of processes and computer programs: A genetic engineer didn't create any of the parts, but the combination of these parts may be novel and nonobvious, and therefore patentable
In addition to giving proper credit to individual inventors, patents help out humanity in general. In the next section, we'll see why patents are so important to a society.