First I got Anime Studio Debut 8 for my birthday.
Later on, I bought Anime Studio Pro 8 when it was on sale (Can't clearly remember what is was. I think around $150). The sale was to promote the release of Anime Studio Pro 9, which was to be a free update to those who bought Pro 8 during the sale. A few months ago, it got upgraded to 9.5 for $50, I think.
And now, just a few days ago, I was notified that Anime Studio 10 will be coming out soon. Hope it's good. :)
...As for how it works...well, try looking up some videos about it. Perhaps ContentParadise on YouTube?
You can also try it in a 30-day free trial.