What is patentable subject matter?
One of the requirements for obtaining a patent is that the invention must be something which is allowed to be patented. So when you are thinking about getting a patent, you have to think about the “subject matter” of your invention to see if it falls within one of the categories of patentable subject matter or whether it is something which cannot be patented.
You can patent a process, which is some method for making something or doing something. More information on processes.
You can patent a machine, which is any device which serves a purpose or performs some task.
You can patent an article of manufacture, which is legalese for a broad category of things which basically includes any device or composition which is made (for example, a tire or a pencil).
Although you cannot patent naturally occurring things, you can patent man-made things. For example, while you could not patent the leaves of different plants, you could patent a pharmaceutical made out of those leaves (as well as the process of making it).
Although you generally cannot patent living things, you can patent certain live matter, such as genetically engineered animals, plants, etc., or the process of extracting a natural product.
You can patent a business method (technically, this is a type of process), which is a method of doing a specific type of business. There used to be a requirement by the PTO that a business method be related to the “technological arts” to be patented - this requirement was generally met, easily, by having the business method be carried out by a computer. However, in October 2005 this requirement was eliminated and certain new guidelines were eventually issued in its place.
You can patent computer software, including the programming method used to create that program. More information on computer software.