How do cells "know" where they are supposed to be in relation to other cells, in forming the physical shape of the body?
If you have ever tried to organise or choreograph the physical positions of a group of people on a field, for example for a dance or display, or even just to stand on stage at a graduation, you will know it takes a bit of communication and working out between the people, and the choreographer (who could be considered a kind of "central intelligence")
Analogy: If you give each person on the field a simple diagram or map (DNA) which shows where the final positions should be, they may or may not be successful, but they would definitely have to talk: "You stand here; I'll be next to you; Jo you need to turn a bit; etc, etc..."
How do cells do this, given than cells could attach and clump in any direction? Especially, how do cells coordinate with other cells quite distant? (Given how small cells are in relation to the shapes & structures of the body)
For example, in my diagram here, 4 cells are forming a specific shape (let's say they're building the corner of an ear or something.) Does cell A "know" where cell C or cell D is?
Please, I'm not after specific chemicals names or in-depth mechanics of cell physiology. I'm after a layman's description or a general principle that is at work.
Bonus related concept: Why/how does the body build a bone of such exact shape the first time around (in the womb) but when you break that bone later, the body seems to just slap bone material around all over, like a bad plasterer?
I've appended a list below of articles I've read (or attempted to read) to try to answer my question.