A region is an area that is differentiated from other area according to certain criteria. In other words, an area having the homogeneity in terms of physical aspects, cultural aspects etc. tropical regions, polar regions. Here the two areas are differentiated by considering climate as criterion.
Functional regions are often Organized around a central point which is also called node. A shopping center surrounded by its neighborhood. Another example would be city and its transit system with suburbs.
The concept of functional region provides a way to examine the linkages and flows that create interdependence among people.