Recorded delivery is an ancillary service provided by the
United States Postal Service for
mail sent outside the country. It's pretty much the
international equivalent of
certified mail, however unlike certified mail, the originating
post office will not keep a record of sending. It's called recorded
delivery for a reason - the destination office hangs on to that record.
Like certified mail, return receipt (the odd looking salmon colored one) and restricted delivery are available. However, you cannot send RD to all countries - only a few dozen, as outlined in the International Mail Manual at http://pe.usps.gov/text/Imm/immc3.html#gnS$w2wats . So if you are inclined to send something to (say) Ireland and need to get a return receipt back for it, you'll have to use registered mail.
Cost for this service is $2.30.