Registered mail is one of the many ancillary services
provided by the United States Postal Service
. It is somewhat related to Certified mail
in one regard - it can be used to track the delivery of an article. This is where the similarity ends, however.
Registered mail is a service to be used for anything of a monetary value, or otherwise requiring secure measures be taken while in transit. The article must be handed to a rural carrier or counter clerk for mailing because this is a secure method of mailing. (Well, OK, it isn't exactly PGP here, but you can't exactly encrypt airline tickets now, can you?) Articles mailed are kept in a safe or with a carrier or clerk during transit (that is, they are not handled with the other mail), and can, for additional fees, be insured for up to $25,000 - or, for even more fees, more than that. Return receipt service is available with this.
This is the protocol you use to mail things like laptop computers, airline tickets, or, in theory, cash - although in any circumstance, putting cash in the mail is not a wise idea. You're better off just spending the money on a postal money order. Either way, this isn't the fastest way to get something from point A to point B, but it's pretty damn secure.
The base fee is $7.50 at this time, with additional fees (no more than about $30) if you insure the article.