in brief, what's confusing me: whenever the transistor is ON, when I can say it's acting like idea switch? for example why when at cmos inverter if vin=5v then we say the output is 0 instantly, why? I know the NMOS switch is conducting at vin=5v and there's a path between "grand" to "output" but who said that NMOS switch in that case is like idea switch "shorted" ?! 
[![enter image description here](https://i.stack.imgur.com/ktj8f.png)](https://i.stack.imgur.com/ktj8f.png)
Moreover, whenever PMOS and NMOS are conducting altogether then we aren't saying that output is 0v or 5v why?! .. what's exactly confusing me is when vin=vdd then we say that NMOS is shorted and PMOS IS OFF, who said that NMOS is shorted? is that because we feed it by vin=5v which he gets the maximum voltage then I assume that switch is act like shorted?

\*\*\* lets assume I have capacitor at Vout (OUT)