"Anonymous" commented on my roving photo of the previous post, asking (I think) if my jacob fiber wasn't actually a carded batt. The photo isn't very clear, it would have been better to see it like this..
Where you can see that yes, it is carded, but it is also in the form of roving, which was rolled up before the photo was taken. If your carded fiber does not come in this form, you can turn a carded batt into a roving (sort of) by tearing it in long strips lengthwise, or drawing it out with your hands like one would pull taffy.
If you get your slivers and your rovings mixed up or just want to learn more, there is a good article by by Abby Franquemont entitled Roving, Top and Sliver in the Winter 07 Spin Off magazine on fiber preparation
It explains the different kinds available and how they are prepared. Spin Off has made this and other articles available in the back issue are of their website in a pdf format (isn't that nice of them?)