The COMMON-LISP package contains the primitives of the Common Lisp system as
defined by this specification. Its external symbols include
all of the defined names (except for defined names in
the KEYWORD package) that are present in the Common Lisp system,
such as car, cdr, *package*, etc.
The COMMON-LISP package has the nickname CL.
The COMMON-LISP package has as external symbols those
symbols enumerated in the figures in Symbols in the COMMON-LISP Package, and no others.
These external symbols are present in the COMMON-LISP package
but their home package need not be the COMMON-LISP package.
For example, the symbol HELP cannot be an external symbol of
the COMMON-LISP package because it is not mentioned in Symbols in the COMMON-LISP Package.
In contrast, the symbol variable
must be an external symbol of the COMMON-LISP package
even though it has no definition
because it is listed in that section
(to support its use as a valid second argument to the function documentation).
The COMMON-LISP package can have additional internal symbols.