What are electrons?

Reviewing the book 'Richard Feynman: A Life in Science', Lee Gruenfeld wrote:

"We think of such things as electrons as, well, THINGS, little point-like particles whizzing around in the space enveloping atoms. But quantum physics shows us that electrons can also be thought of as waves, little different from light waves. So which is it, really? The answer, really, is that an electron isn't really much of anything until we do something to make it pop up in one of its two forms, wave or particle. Otherwise, it's just hanging around in a phantom zone of marginal reality with no real objective form at all. 

Truly ... quantum particles are the dreams that stuff is made of".