Having EE as a real life background, I can answer a few questions for folks.
The parts...
Voltage: measure of electromotive force (how hard it's pushing)
Amperage: measure of current flow (bigger is badder)
Power: measured in Watts. It is a summary of just how much power is flowing.
DC: direct current. It has no waveform. Think of the power coming from a battery.
AC: alternating current. It does have a waveform (typically sinusoidal, can be different).
Those terms aside, the hallmarks of DC is that once you get hit with it, it causes your muscles to freeze. In a typical action like bending your arm, you have some muscles contracting while others are relaxing (in a push/pull setup). DC will make all those muscles contract at the same time. That makes your arm lock.
DC is bad ju-ju when it comes to getting shocked, especially if it crosses your heart (like getting shocked from hand to hand). See above for why and keep in mind that your heart is a muscle.
Getting shocked by AC is bad in its own way. Ever hear the phrase "60 cycle shuffle"? It's a bad dance move performed by those getting shocked by 60 hz AC (typical household power outlet in the US). Just so happens to be a bad frequency for our bodies (our hearts don't like that frequency much). AC works just like DC... except it makes your muscles relax & contract at the frequency of the line power (60 cycle shuffle?). AC has a higher propensity to throw you than DC does in most cases but you can be thrown (across the room) by DC as well. Depending on what you are doing, you may end up hanging onto your equipment when you'd rather let go.
I can't speak for tasers but a classmate in HS Electronics (vocational school) shocked himself with 50k Volts DC at 1 microamp (0.1 milliamp). It froze his arm (to his elbow) and hand for about 10 minutes before he could start moving them again. He said it hurt like hell and that he couldn't feel his arm for the duration.
I have personally taken 440 Volts AC from elbow to wrist off a bridge rectifier in a floor TV power supply. Blew out the Bridge rectifier and the zap also threw my arm away from the tv console.
Generally if one is using electricity to incapacitate, you want to use a high enough voltage to cause conduction. Between 5k and 50k Volts is often enough (depends on desired target audience, heh). You only use enough amperage to cause the desired pain / stunning / numbness. Generally this will be a low number (less than one milliamp).
Against someone like me (100+ Meg Ohms of skin resistance aka 100,000,000+ Ohms of skin resistance), you'd want at least 10k Volts in order to generate conduction. At 10k Volts, all you'd get for current flow is 0.1 milliamps. Certainly enough to piss me off. 50k Volts would get you 0.5 milliamps which would be significantly more incapacitating. Zap it down the line with AC and you'll have me dancing & twitching.
The bad part is that a low amperage is quite capable of killing you. We had a chart on our wall that showed the effects of amps of current flow. According to the chart, 5 milliamps was enough to kill you. The bad part shown on the chart? Get to 1+ amps and you get to live while cooking (until you die).
For those that want to know, Power = Amps * Volts so... 1 Watt = 1 amp * 1 Volt.
Also, Ohm's law states that Current = Voltage / Resistance so... 1 amp = 1 volt / 1 Ohm.
In summary, electricity is serious business. It can fuck you up. It also makes for a hell of a modern convenience.

*edit for a few typos