Tài liệu PL/SQL User’s Guide and Reference phần 8

expression
This is an arbitrarily complex combination of variables, constants, literals,
operators, and function calls. The simplest expression consists of a single variable.
When the declaration is elaborated, the value of expression is assigned to the
parameter. The value and the parameter must have compatible datatypes.
parameter_name
This identifies a cursor parameter; that is, a variable declared as the formal
parameter of a cursor. A cursor parameter can appear in a query wherever a
constant can appear. The formal parameters of a cursor must be IN parameters. The
query can also reference other PL/SQL variables within its scope.