For example, let's look at this big ball, right? So inside this ball we have air. And if you were to push this guy in, I could easily to some point push this ball in. Now, if this, if the inside was replaced with, say, salad or liquid, I wouldn't be able to push it without changing the volume. Notice how when I'm pushing this I'm not really affecting the volume too much, right? And that's why I'm able to push it, I'm compressing it.