I don't know what your experience with remote aerial vehicles, and flight controllers is, but as JasonK mentions, it sounds like you're starting to learn about them. Think about the problem you want to solve as similar to your use of computers. It's a very similar relationship to a single computer acting alone and a networked computer working with one other or more computers. If you have a single computer not connected to anything else, that's the same as a stand-alone UAS. If you want to network them, let's say for multiplayer computer games, or other such purposes, then you need to set the computers up to be able to communicate with each other or a central controller/server. Think peer to peer networks or a server based multiplayer video game. I use gaming / computers as an analogy because most people are familiar with those concepts, particularly when you are using a web browser to post to forums
Of course, as with any technology, there are many ways to solve a problem. One could have UAS's be aware of each other without a direct connection to each other, by increasing the autonomy of them and having sensors that allow for them to "see" other UAS's and objects.