ELI5 Starlink - what makes it possible and how does it work?

What is low earth orbit and how does it enable Starlink to deliver high quality internet? Do they need regulatory approval to operate in each country? With so many satellites, space debris and the risk of collisions must be a major concern - how does SpaceX manage these risks? Weren’t there some near misses early on?
... we explain like I'm five
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