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.