Some people have ideas about how to make or do new things, or how to do known things better, and spend a lot of time and, often, money, getting those ideas to work to make something that helps others. I help these people stop other people from using those ideas without asking, for some time, so that they can make back the money they have spent, and get some more money for having had the good idea and spending all the time needed to make it work. After a while (at most about twenty one years) anyone is allowed to use the idea as much as they want to, even without asking the person who first had the idea, which is good for everyone.
In order to be able to stop other people using the idea (without asking the person who first had it) the idea must have been new, and must not have been too easy for other people (even people who knew a lot about the area of the idea) to have arrived at, at the time when we first asked to be allowed to stop other people from using it without asking. Also, we must tell everyone exactly how to make the idea work, so that anyone can do it easily when the twenty one years are over. I help to find out what it is about the idea that is new, and to explain to everyone, in writing, exactly how to make the idea work, and that they may not use the new bit without asking.
Daniel Rosenthal, patent attorney. (via tenhundredwordsofscience)
Patent law explained in plain English.