Behind the scenes, every Aurora server connects to HC Net Core, the backbone of the HC Net. The HC Net Core software does the hard work of validating and agreeing with other instances of Core on the status of every transaction through the Federated Byzantine Agreement (FBA). The HC Net itself is a collection of connected HC Net Cores run by various individuals and entities around the world. Some instances have a Aurora server you can communicate with, while others exist only to add reliability to the overall network.

You might want to host your own instance of HC Net Core in order to submit transactions without depending on a third party, have more control over who to trust, or simply to help make the HC Net more reliable and robust for others.