What's to explain?
Force lightning (better known as Sith Lightning) is just a very advanced force move, you just have to be powerful enough to do it.
The reason you only see Sith do it is because they took the easy way of the force (the dark-side) and it gives them easier access to power.
A Jedi must train for a very long time or have high midichlorians to be able to do something like that.
That seems quite speculative, Lance. And I don't think we should be distracted by the Lightsabre, Obi-Wan could stop it which is demonstrative of the fact that it is NOT hard to stop- you don't have to be Yoda.
We don't really know much about it other than we have only seen bad guys use it, but that could mean anything.
It really doesn't seem that useful to me...
The force lightning are a agressive move, Jedis were defensive in their ways guess thats why they dont use it. After Dooku used it on Anakin the surprise was gone and Obi had no problem blocking it. Even if it was sucker move again t Yoda he didnt have any problems with it. So if you are aware of it it doesnt look affective at all.