Where can I learn more about portals?
There are several things I would like to know about them:
1. Who can open a portal? How?
2. Who can close a portal? How?
3. Can portals be opened in any type of region or only in some specific types of region?
4. Is there one or more types of portal?
5. Are portals one way/two way/multi way?
6. What is use of portals?