Flobberworms are small, docile slime producing worms. They are rated X by the ministry of magic. Which means boring because they prefer to be left alone and require almost no care except to be careful not to over feed them. They eat vegetables like common garden snails and slugs do. After the hippogriff attacked Malfoy Hagrid lost the will to teach and resorted to using Flobberworms for the OWLS exam, the purpose was to keep one's Flobberworm alive until the end of the lesson. Ron spent the exam trying to force feed his worm lettuce into its rear end mistaking it for its mouth.
The school sometimes serves Flobberworms as Flobberworm fritters at lunch, much to the pupils disgust.
Flobberworm mucus is used in potions such as the stamina potion. It is used to thicken mixtures.