"discontinuous affixes"

I've been working on a little conlang called "Slohun," and I
happen to have a copy of Greenberg's list of 45 linguistic universals
(it's published in an encyclopedia of language and linguistics
whose title I can't remember because all I have with me is a
photocopy of the relevant bits.)

Anyway, universals 26-27 are:

"If a language has discontinuous affixes, it always has either
prefixing or suffixing or both."

"If a language is exclusively suffixing, it is pospositional;
if it is exclusively prefixing, it is prepositional."

My firsthand linguistic knowledge is pretty slim, and pretty
limited to prepositional languages, such as Latin and English
(unless you count very old Greek).

I'm not sure what they mean by "discontinuous affixes" here...
are those things like prepositions used as part of a verb, such
as "pre+pono"?  That would explain why they are associated with
prepositions, if that's what they are.

But does anyone know the technical definition of a "discontinuous
affix"?  Or, for that matter, "prefixing" and "suffixing" as
used in the paragraphs above?

Ed

-----
MailStart Plus - http://www.mailstartplus.com
Consolidate Your Mailboxes Into an Organized, Filtered, Spell-Checked,
Anywhere, Anytime WebBox