Interoperability can mean many things.
Interoperability is one of those words that conjures up very different visuals for each of us. Paper cups attached by string, the WiFi router in your home, the towers and satellites that allow your text to be sent across the world in milliseconds, and the NASA space station, are all examples of interoperability.
In healthcare, it might mean electronically receiving the lab order from the doctor’s office, or aggregating and sharing in target-system-ese, the problems, meds, and allergies of every patient in Massachusetts.
Some might say the term interoperability is overused, but it’s shorter than saying, “take thousands of proprietary systems that were created as good ol', 'stand-alone, I don’t need anyone, I am king of the hill, you can’t boss me around,' and make them share information.”