The little balls that are in Tapioca are starch that is extracted from the cassava root which are translucent spheres produced from the Tapioca.
The little balls that are in Tapioca are sometimes also called Tapioca Pearls or just Tapioca Balls.
The Tapioca balls or Tapioca Pearls are usually the size of marbles or peas.
It's been reported that sometimes the tapioca pearls or tapioca balls release chemicals that can lead to some cancers in some people.
However there's not much evidence of that and many people consume the tapioca as well as tapioca pearls without any health issues.