Diff b/w Package Spec & Body

Packages provide a method of encapsulating and storing related procedures, functions and other package constructs as a unit in the database. They offer increased functionality (for example, global package variables can be declared and used by any procedure in the package). They also improve performance (for example, all objects of the package are parsed, compiled, and loaded into memory once).

Package specification contains declarations of public constructs where as the package body contains definitions of all those public constructs and declarations & definitions of private constructs.