A simple way to understand the diffusion/osmosis concept

Well to me, probably the simplest way to understand the concept of diffusion is this:
What happens when someone just rips one in class? Well, the person who dealt it smells it first (whether they admit it or not). Next, other people (the victims) close to that person start pulling their shirts up over their nose to block the awful smell. But then, someone will walk by and comment on a funky smell, but wouldn't have ever known how terrible it was at first, or even what caused the stink. And eventually, no one smells it anymore. Why?
It's because diffusion works in the air around us too. Diffusion just means that areas that have a lot of something move to areas that don't have much. So at first in the example above, all the smell is concentrated in one area, right? And then it spreads out, until the point where it's not even smell-able anymore. This is diffusion. And osmosis? Well, this is just a fancy word for the same thing, just with water. Hope this helps. If not, sorry you had to read all this ;)