Here is a logic AND gate.   I will start out with a premise:

0 – 2.5V is False.   
2.5+ to 5V is True  (  2.5000001 or greater )

V1V2Vout
000
010
100
111

This is an example of a circuit with an AND Gate.   Both switches are in series.  So when both our 1 or On, V1 goes to 5V.  If both or one are off, no voltage reaches V1 because the circuit is open. 

We start with 5V and 5V this shows 5V for output

We start with 5V and 0V this shows 0V for output

We start with 5V and 2.5V this shows 0V for output

Now we get just above 2.5 and we get a 5V output