Okay, so imagine you're playing with blocks and you have instructions on how to build a tower. You follow those instructions step-by-step and your tower looks just like the picture in the instructions.
Now, a knowledge-based processor is like a brain for a computer that can follow instructions like that tower-building example. It has all sorts of information stored in it, kind of like a big library. Whenever the processor needs to do something, it can search through that library for instructions on how to do it.
So let's say you want to use your computer to edit a photo. You don't know how to do it, but your computer's knowledge-based processor has stored information on how to do it. When you click on the photo editing software, the processor goes into the library and finds the right instructions on how to edit a photo.
Overall, a knowledge-based processor is pretty smart because it has a lot of information stored up and can use that information to do lots of different things, just like you can use your instructions to build different things with your blocks.