For questions relating to the legal requirements necessary for applications to be granted a patent. Please include a tag relating to the relevant type of intellectual property protection you are asking about. There are invention patents, design patents and utility models. For an explanation of the differences, read the full tag description.
The basic requirements for an invention to be patentable as an invention patent are
- inventive step
- industrial applicability.
Novelty means that the same invention has not been published (or presented as a patent application) anywhere before the date of the application.
Inventive step is fulfilled if the invention does not follow obviously from the known prior art for a person skilled in the art (i.e. somebody usually asked to solve the respective problem).
Lack of industrial applicability is used against inventions like perpetuum mobiles as they are not d'accord with known laws of physics and therefore not usable in industry (because they are impossible to build/use). It's sometimes called usability too.
The formal requirements can be looked up on the webpages of the patent office for the country the patent is applied for in. In the US this would be the USPTO.
Follow this link for a formal description: https://www.uspto.gov/web/offices/pac/mpep/s2104.html Or consult wikipedia: https://en.wikipedia.org/wiki/Patentability
"Types of patents" There are different types of intellectual property rights that are sometimes called three types of patents, though formally that's not correct.
There invention patents, utility models (not in all countries) and design patents. Please relate to the relevant tags or google for more information.