It goes beyond coordination and communication, as a lot of people will suggest. These are important though, it's not like if you throw 5 dudes who know each other into a call they'll be able to perform at the level of pros in these aspects.
I'm going to touch on two different things here.
FIrstly, they [have analysts] do research to plan around minute details of player behavior. Like, "Oh, top lane player X goes down to ward the pixel bush at 6 minutes every game. We should be there to trap him." or "In ABC matchup, mid player Y tends to hover to the left side of mid lane. How can we take advantage of that?"
Another thing is creating gameplans. In solo queue each individual challenger player should have a good idea about power spikes, win conditions, etc. I'm talking smaller things. Like "When Baron gets to 2k HP we're going to burst and smite." or "When Baron gets to 2k HP we're going to turn and engage on X player/closest player." Things like that.
The overarching details, like communication and coordination are certainly important. You will see teams without these things cough Echo Fox's first week with Mike Yeung cough and they tend to get absolutely pummeled, but you could throw a group of high level challenger players together and they will perform these tasks at a reasonable level together in solo queue. What really sets pro matches apart from solo queue is the tiny, intricate details they use to try and get an edge.
A great [mis]quote I (kind of) remember from Day9...and bear with me, it's been like 10 years since I heard this....when regarding SC2. "[Click and drag] boxing units from top left to bottom right or from bottom left to top right might increase you from the 2nd best player in the world to the 1st....but it's not going to do anything for 99.9% of players."
