Tapioca/Arrowroot starch/flour, in the Australia are interchangeable. The label on the arrowroot in the supermarket will probably say made from tapioca.

Arrowroot is a starch obtained from the rhizomes (rootstock) of several tropical plants, traditionally Maranta arundinacea, but also Florida arrowroot from Zamia integrifolia, and tapioca from cassava (Manihot esculenta), which is often labelled as arrowroot. Japanese arrowroot, Pueraria lobata, also called kuzu, is used in similar ways

Tapioca starch is the purified starch portion from the cassava root.
Tapioca flour would traditionally encompass processing the whole root (and thus capturing the fiber).  There is a new product made with the fiber and to avoid confusion is called Premium Cassava Flour (designed for gluten free baking) and called so to avoid the current tapioca flour confusion.

Cassava is the plant from which tapioca is extracted.