A patent is limited in terms of time, geography and technology. Normally the patent expires 20 years from the date of filing. In reality patents often expire earlier due to the fact that patent proprietors in many cases decide not to pay maintenance fees. Furthermore, a patent can be invalidated, e.g. if it is shown that the invention lacks novelty.
A patent basically applies to a single country, but there are also regional patents, such as European patents. However, European patents must be validated individually with authorities of the respective countries to get valid patent protection. At present, there is no “world patent” that can be enforced worldwide. Enforcement of a patent needs to be carried out in each individual country. It is possible to reduce the number of lawsuits for example by starting proceedings in a country where production takes place.
The scope of protection conferred by the patent is determined solely by the claims in the patent. The claims are usually found at the end of the patent document. The description and state of the art constitute a supplement to interpretate the claims.
It must be noted that a patent must be issued before it can be enforced. A patent application will often have broader claims than a granted patent, and several ongoing patent applications will have their broad claims severely narrowed if they become granted patents.
In the event of infringement, it is the patent proprietor or licensee themselves who must file a lawsuit.