What's the regions?

In Geography, regions are areas that are broadly divided by physical characteristics, human impact characteristics, and the interaction of humanity and the environment. Sorry didn't realize it was for math

In mathematical analysis, the word region usually refers to a subset of or that is open (in the standard Euclidean topology), connected and non-empty. A closed region is sometimes defined to be the closure of a region. Regions and closed regions are often used as domains of functions or differential equations.

Step-by-step explanation:

(I got this from the internet.)