In a parallel circuit, why is the voltage the same anywhere in the circuit?

Answer 1

Wikipedia has a really good article on the hydraulic analogy that's sometimes used to explain electric current.

In essence, the current (amperage) is the number of electrons flowing through the circuit, and the voltage is the difference in pressure at a specific point.

In a series circuit, you have full current, but half voltage, because half the voltage is used on the first bulb, and half on the second.

In a parallel circuit, you have half current going to each bulb, but that current uses full voltage on the one bulb it's lighting.