Why are people talking about the NBA trade with Luka doncic and Anthony Davis?

https://www.reddit.com/r/nba/comments/1ifpz94/charania_breaking_the_dallas_mavericks_are/

a lot of comments I read on this topic (YouTube, Reddit) says that this is "the most shocking news they've ever heard" or that it's "unbelievable" and "doesn't make sense"

I have never been one who is into to basketball or any kind of sports, but For some reason the collective "this is INSANE" discussion from the sports community has me interested.

So as an outsider to basketball, what is a trade in the nba, and what's the big deal with this trade. Who benefits the most from this trade and why is this trade so unbelievable?