It's so insane that he links to a whole another post to clarify what he means by "the edge", and he struggles to state that in the first 5 paragraphs of it.
Well, the post "about the edge" also links to some announcement post there they "tried" to talk about the edge in more edgy details. Yet, it's like paragraph 67 on that 3rd post they were mention something about "the edge".
It's the datacenter closest to your user(s) where you deploy services that require minimal latency. That's all there is to it.
A computing platform with intermittent and/or slow network connectivity?
I would say "low computing power" but a raspberry pi is 4Ghz these days.