Details regarding PMOS and NMOS transistors used as gates
is PMOS the same as PNP? (and NMOS same as NPN)?

No.  PMOS and NMOS are types of field-effect transistors (often called FETs, the most common type of which is MOSFET).  PNP and NPN are types of bipolar junction transistors (often shortened to BJT).  An NMOS transistor is analogous to an NPN, but they are by no means the same.

How do they actually work as &quot;gates&quot;? how does it relate to the input given and the actual properties of these transistors?

&quot;Gate&quot; is a poor choice of wording, because the control terminal on a FET is called the &quot;gate&quot;.
Transistors work as switches because when you put a low-powered signal on their control terminal (gate for FETs, base for bipolars) the transistor will switch from off to on, and can control orders of magnitude more power at its active terminal than you put into its control terminal.
(Sorry for all the abstract language -- I'm trying to cover both FETs and BJTs here).
You should look this up -- Wikipedia is a good place to start -- there is a lot of information out there.

What do Logical 0 and 1 really represent? (as voltages).

Any two distinct voltages can be labeled as being 0 and 1 (or false and true, or 'apple' and 'orange').  Typically, in modern usage, a voltage close to the positive supply is considered a 1 and a voltage close to the negative supply is considered a 0.
Whether to map high voltage to 1 or 0 and low voltage to the other is up to the circuit designer -- and, these days, to the mob of young engineers with torches and pitchforks who will assemble if you choose anything other than high = 1 and low = 0.