Adding the "dot" before a command name

Can someone please tell me what the . before a command name means?
ie. (command ".rectangle"

Adding the "dot" before a command name ensures that the generic AutoCAD command will be used instead of one that might be
substituted (or missing) by virtue of the command having been undefined. You might also see/use (command "_.LIST" ...) wherein the
underscore ensures that the command will be recognized by its English language despite the actual language being used.

An good example of the "dot" usage is within Land Desktop where the "NEW" and "OPEN" commands have been undefined and replaced with
"AECNEW" and AECOPEN" respectively. To circumvent these specialized commands, one can enter ".New" or ".Open" at the command prompt
to issuse the generic AutoCAD version of each.

If you develop AutoLISP programs that can be used with a foreign language
version of AutoCAD, the standard AutoCAD commands and keywords are
automatically translated if you precede each command or keyword with an
underscore (_).

(command "_line" pt1 pt2 pt3 "_c")
If you are using the dot prefix (to avoid using redefined commands), you can
place the dot and underscore in either order. Both "._line" and "_.line" are
valid.