According to Foster, what is a myth?

From the text:

What we mean in speaking of “myth” in general is story, the ability of story to explain ourselves to ourselves in ways that physics, philosophy, mathematics, chemistry – all very highly useful and informative in their own right – can’t. That explanation takes the shape of stories that are deeply ingrained in our group memory, that shape our culture and are in turn shaped by it, that constitute a way of seeing by which we read the world and, ultimately, ourselves. Let’s say it this way: myth is a body of story that matters.