A patent is a publication that describes how to make and use an invention. A patent further defines aspects of the invention that the inventor has excusionary rights to. These definitions are called "claims". Patent rights are granted by nations. Patents, therefore, are enforceable only on a nation by nation basis.
An inventor has the right to stop anyone from making, using or selling the claimed invention. These rights are enforced through civil lawsuits. In the US, an inventor has the right to collect the minimum of a reasonable royalty or lost profits that were due to a person or company infringing the claims. The inventor also has the right to stop the infringer from continuing to practice the claimed invention.
Patent rights last for a limited period of time. In the US, patent rights last from 20 years from the date a patent application is filed.
Patent claims are examined in most countries. A patent examiner who works for a patent office is assigned to a patent application. The patent examiner reads the application, reads the claims and then searches for earlier publications that either teach or suggest the claimed invention. If the examiner finds references that teach the invention, then the claims are rejected. An inventor can then change the claims or provide counter arguments as to why the earlier publications do not teach the invention.
If the examiner cannot find a single reference or combination of references that teach the invention, then the examiner will allow the claims.
Patents are property. The ownership of a patent originally vests with the inventor(s). The inventors may assign their ownership rights to another person or company. It is common for inventors that work for a company to assign their ownership to the company they work for.
Patents may be licensed. A patent owner will agree not to sue an infringer in exchange for certain considerations from the infringer. These considerations often include monetary payments.