We now come across another Lisp feature, read-delimited-list.  This function is generally expected to be used in the construction of reader macros.  You might want to review the discussion of reader macros under gensym and get-dispatch-macro-character.  You would use it to build a reader macro that interprets a sequence of objects between bounding characters as being a list.  The standard reader macro for the #\( character could invoke (read-delimited-list #\)) to retrieve the list between the parentheses.

Because this function doesn’t have any resilience for handling bad cases, it is fairly brittle, and so I would tend to discourage its use in other contexts where the input stream format is less rigidly enforced.