lisp question

[Hadron]

from the lisp tutorial which comes with emacs 22:

,----
| 1.8.3 Variable Number of Arguments
| ----------------------------------
| 
| Some functions, such as `concat', `+' or `*', take any number of
| arguments.  (The `*' is the symbol for multiplication.)  This can be
| seen by evaluating each of the following expressions in the usual way.
| What you will see in the echo area is printed in this text after `=>',
| which you may read as `evaluates to'.
| 
|    In the first set, the functions have no arguments:
| 
|      (+)       => 0
| 
|      (*)       => 1
| 
|    In this set, the functions have one argument each:
| 
|      (+ 3)     => 3
| 
|      (* 3)     => 3
| 
|    In this set, the functions have three arguments each:
| 
|      (+ 3 4 5) => 12
| 
|      (* 3 4 5) => 60
`----

It kind of glosses over sections (1) and (2).

Why do (*) and (* 3) evaluate to 1?