The command and form presentation types are complex types provided primarily for use by the top-level interactor of an application.
expression
Summary: The presentation type used to represent any Lisp object. The textual view of this type looks like what the standard print and read functions produce and accept. The standard print and read functions produce and accept the textual view of this type.
A separate presentation history for each instance of an application frame is maintained for the expression presentation type.
form
Summary: The presentation type used to represent a Lisp form. This is a subtype of expression and is equivalent to it, except that some presentation translators produce quote forms.
command
Summary: The presentation type used to represent a command processor command and its arguments.
A separate presentation history for each instance of an application frame is maintained for the command presentation type.
command-name
Summary: The presentation type used to represent the name of a command processor command in the command table command-table .
command-or-form
Summary: The presentation type used to represent either a Lisp form or a command processor command and its arguments.
Common Lisp Interface Manager 2.0 User's Guide - 20 Sep 2011