Not stupid. I had to ask the same question.
Yes, it is cooked shrimp. It comes in the little tiny ones or in bigger sizes that I think they call tiger shrimp. I have used both, but the bigger ones I have to cut up more. I cut it up before I freeze it, then flatten out the baggie and lay it on the freezer shelf, that way it doesn't freeze into a big hard uncuttable rock of shrimp! I learned that lesson early on. Once it's frozen, it doesn't have to lay flat.
You can also use freeze-dried krill on a feeding stick. Do you have a feeding stick? The lfs
may have long thin hard tubing, just get one of those and push a peice of a wooden skewer into the end. That way you can stick the shrimp on there. I used a wooden toothpick, but had to kind of flatten the tube around it because it's wider, but it works. I also bent one end of my tube and put a toothpic in that end so that I can have the angle necessary to reach the shrimp under the rocks a little if need be, otherwise my fish try to eat it off before Mr. I'm So Slow starfish gets around to it.