Hmm, it seems the description should a bit more clear then. Let me try to explain and let me know if that works for you!
A/B testing is basically testing different variations of a page. So you have a page that looks just like it looks now, but you feel something can be improved to get more sales or signups, or maybe just more engaged users. With this plugin and the Convert Experiments tool, you can create a variation of your page, without having to change the URL. 50% of the users will get the original page, and 50% will get the "new" page, with all the things you changed. And they all go to the same URL, so users won't actually notice anything.
Within the Convert Experiments tool, you can see the results (live!) and actually see which page variation is performing best.
Did that help clarify?
My advice: just download the plugin and try it all out! It's free anyway! ;)