When I read unity official website information:
20+ different platforms run Unity creations
What’s the meaning of this sentence?
please give an example of platform to explain it.
Here is a list of platforms Unity supports:
https://support.unity.com/hc/en-us/articles/206336795-What-platforms-are-supported-by-Unity-
In computer technology a platform is essentially any software or hardware environment that runs apps. For PC it is more complex as there are multiple software platforms available. Examples of software platforms are Windows and Android. Examples of hardware platforms are Xbox Series S/X and Nintendo Switch.