Would not it be great if all this could be done with the click of a mouse button ? Ok, some more clicks but still a lot less than performing all those tasks by hand one after another. You will have to record the task(s) once which simply involves starting the extension and moving, typing and writing exactly as you always do. Selenium records all action and you are able to save it afterwards.

You´ll unfortunatly have to load it whenever you want to replay the task. It therefor makes only sense to me to record and save tasks that involve lots of writing, moving and clicking. Maybe there is a way to store them in your Bookmarks toolbar but I have not found a way to do so. It would be awesome if this would be possible. (Bare with me, I´am using the extension for 10 minutes..)

Seleniums main purpose is web application testing. It (not the firefox extension of course) runs in most popular browsers including Internet Explorer, Firefox and Opera. Instead of looking at / or testing webpages in different browsers you record the task once and play it in every browser afterwards.
Take a look at a presentation video of selenium ide that shows how to record and play tasks.