It generally means model running in parallel with the actual system. It is not just about being able to store data, but about being able to mirror (and sometimes predict/replicate) exactly what that system is doing.
In current software parlance, this is often used in stupidly trivial ways, but digital twins have a long and important history and function
In current software parlance, this is often used in stupidly trivial ways, but digital twins have a long and important history and function
https://en.wikipedia.org/wiki/Digital_twin