Patency is what all originators companies depends on in their business
simply its the company's rights to have the manufacturing rights for a well known period of time.
in that period "which is well known by the local law" no one can manufacture or sell this product unless its through a legal contract with the original company
after loosing the patency any company or factory can make the product and sell it then what these companies manufacture is known by "Generics"
pfizer are facing a huge financial problems this year, because they lost one of the most important and profitable product's patency