This graphic shows one tablespace that contains two datafiles. The datafiles area the physical structures associated with only one tablespace. Inside the datafiles are objects, like tables and indexes. One table is shown spanning two datafiles.
One caption points to both datafiles. The caption says "Datafiles are physical structures associated with only one tablespace." The segments caption points to a table and index object. The caption says "Segments are stored in tablespaces and may span several datafiles."