Patents were intended to encourage invention by providing a short term period where no one can make money after your invention. In exchange, you revealed how the invention was made and when the patent expired, it became the property of everyone. Patents are a balancing act – one side benefit individuals, on the other the benefit the public. When the balance tips too far in either direction we get less invention.
This system has always had its problems because patents are powerful so there were many bitter disputes between competitors. But when a new kind of technology called software started to get patented things began to get strange.
Unlike many older inventions software isn’t a machine. Its functions are trickier to define and some patent holders have taken advantage of this and laid claim to broad features that should have never been patented. The combination of and old law and a new technology presented a lucrative opportunity to exploit the power patents and a new kind of corporation took advantage: the patent troll. Patent trolls are mysterious corporations that file law suits or demand licensing fees in order to profit from broad patents. They often go after small software developers who can afford expensive law suits, so the developer ends up paying a licensing fee just to avoid going to court.