If you want to know how UPnP works in general, you might want to check up this Wikipedia page: Universal Plug and Play. As a user, there are three things you can control: what external ports are allowed, which internal IP addresses are allowed, and what internal ports are allowed. You almost always want to check the three checkboxes on the left for enhanced security – unless it breaks some application you really need working.
When you put a restriction in parental control, you block the user from visiting certain web sites. It doesn’t do anything to the WiFi. You still connect to the WiFi as usual, but you won’t be able to visit web sites when they are blocked. When you enter a calendar, your access to the Internet (or web sites listed in the calendar) is blocked outside the time range allowed by the calendar. Even though you are connected to the WiFi as usual.