This is a grindal worm starter culture! I take it from my own culture from my fish room.
Grindal worms can be kept in many different ways. I use damp organic potting soil as my substrate and I feed my worms a variety of food like old fish food, dog kibble, or bread. I sterilize my soil (microwave!) and let it fully cool before adding my worms, and I also microwave foods before giving it to them to make sure there aren’t any mites.
You will be receiving a baggie of my grindal culture which you will need to add to a container of your own. If it seems like no worms survived shipping, just keep it damp in a warm place,feed tiny amount of food (remove/replace before mold appears) and you will notice them start to come back.