So I looked through some other posts, and I got a sense that a slider is a small burger, White Castle size. Except there are some places around where I live that sell burgers that people call sliders, and they're not particularly small. They're greasy, delicious, wrapped in waxed paper, but they seem pretty normal-size. So what, officially, makes a slider a slider? And why the name? 'Cause they slide right down? Help!