What makes olive oil extra virgin? Why is it called that? Also...what about the other varieties?

I do a lot of cooking with olive oil and just got to thinking...why on earth is it 'virgin'? lol. everything calls for extra virgin olive oil...and when I was at the store I saw 'light' and 'extra light' aswell. Why are they categorized as they are???What makes olive oil extra virgin? Why is it called that? Also...what about the other varieties?
';Val'; is right, the frist pressing is the finest quality, then the next 2-4 pressings have either to be heated to extract all the old up to a point were the olive mash is mixed with a neutral oil and when it settles it is strained off and that is were the Pomice/Pumice oil comes from, it is just olive flavoured veg oil but nice for cooking or bulk salad dressings.





The Light and Extra light are just diluted with a soya or veg oil to lighten there taste and calorie content, not really what I would have used when a chef, for salads and appetizers the best available, I actually prefer Greek or Sicilain over the expensive Italian ones, there are lots out ther from Spain, Portugal, Lebanon, Syria and France all like wine have different complexitys, I always used Spanish Gallo for cooking and Krinos Greek for other things, I just like the taste.What makes olive oil extra virgin? Why is it called that? Also...what about the other varieties?
Extra virgin olive oil means its from the first press of the olive. meaning its the purest. as far as the light and extra light im not sure. rachel ray didnt go that in depth when she explained em lol
It is purified more and has a nuttier taste.