I'm afraid I'm going to have to disagree a wee bit with what some of you are saying about the eighth notes. My guess is that you wouldn't be saying that if there hasn't been, over the years, the emphasis of the triple feel against the duple feel to describe swing. I mean, when people were playing square, the first way to get them out of that was to explain that in swing you don't play the eighths straight but you play them more in a triple feel. And by comparison to straight eights, that's pretty much true. I mean, think about it. What else are you going to tell them?
So now, after decades of people being told that you don't play eights straight, you play them with a triple feel, people are saying, "yeah, wellll, not realllyyy?" and that's right too. And the faster it goes, the straighter they become. But you listen to Basie playing a typical Nestico chart and they are hardly playing straight eights on medium tempo charts.
So I would recommend a little caution about how and when we tell people that eighth notes really don't have a triple feel to them because in comparison to straight eight notes they do. IMO it's all in context.
Now what swings? Here - this swings: