Types are Index -by- table Nested Tables and Varray!

plsql supports mainly 3 types of collections
1> index by binary_integer
2> nested table
3>varrays
index by binary_integer and nested table are collectivily known as plsql tables
and nested table and varray can be stored in database table but index by binary_integer cant be stored in database table

the syntax for index by binary_integer
ex: declare
type basu is table of varchar2(10)
index by binary_integer;
if you leave the key word binary_integer it becomes nested table
ex: declare
type basu is table of varchar2(10);
the syntax for varrays is
ex: declare
type basu is varray(5) of varchar2(10);