A package is a group of logically related procedures, functions, variables, and SQL statements created as a single unit. A package is a schema object just like a table and a sequence. A package has two parts, package specification and package body.
A package specification does not contain any code. You typically declare variables, constants, cursors, procedures, and functions in a package. A package body is used to provide the implementation details. All the program logic is coded in the body. Within the package specification, we can specify which subprograms are visible to the public and which are not (private). By hiding implementation details from users, you can protect the integrity of the package.
Stored subprograms defined within a package are known as packaged subprograms.