Difference in olive oils?

Since we are now cooking our meals from scratch, I am finding myself using oils a lot more. So I had to learn what the difference was between the olive oils (regular, virgin, and extra virgin). After looking at many, many different sites, they all basically said the same thing. So I just copied the answers from one of the sites and here is the jist of what the difference is.......

What is ‘Olive Oil’
A. Olive oil is olive juice, plain and simple.

What is ‘Virgin?’
A. Virgin means mechanical extraction. The oil or juice is extracted by machines with no chemicals used in the process.

What is ‘Extra’?
A. Mechanically extracted (virgin) olive oil is not all the same quality. 'Extra' is the highest quality and is thus classified because it goes through a battery of tests, both laboratory (analytical) as well as 'taste' (a cutting by an olive oil master similar to the way wines are taste tested). Virgin olive oil that is judged to have ‘no defects’ is classified as extra. So ‘extra virgin’ means – mechanically extracted olive juice that passes laboratory and taste testing with no defects


So basically it is saying to spend a little extra and buy the extra virgin. I also read to make sure it is stored in a glass bottle because if it is stored in plastic container it can absorb PVCs. It also needs to be stored in a cool, dark place away from heat of the stove and sunlight.
Hopefully this helps you as much as it has helped me better understand olive oils.