A patent, when granted, allows you to stop someone else from using your invention. Some truely absurd patents have been awarded over the years, such as the use of a laser pointer as a cat toy, or a toy for any animal with a hunt reflex. This could be challenged by anyone 'skilled in the art' of playing with cats on the grounds of obviousness, but it was still granted. Makers of laser pointers can still sell their wares, but if they promote them as cat toys they may be infringing.

Quite frankly, patents are a complete quagmire to suck in the unwary. Big corporations have the resources to patent everything, and they then use them as bargaining counters in patent disputes. They put a typical value of $10,000 US on every patent in their portfolio, which they then cross license. The idea that every patent is worth the same amount is clearly nonsense, but more practical than assessing them indiviually.