SSL stands for Secure Sockets Layer
, and it is the encryption scheme that is used when you, say, connect to a secure web-site ... one whose URL begins with https//
OpenSSL is an open-source implementation of SSL and, as such, is pretty much the definitive
one at this point. The advantages of openness in a security product are fairly obvious, and compelling: you can literally "see for yourself" what is being done with your data.
The SSL suite is a fully-featured encryption scheme, and
a "digital certificate" scheme that enables the reliable authentication and verification of who
is talking to whom
. The OpenSSL web site
contains a great deal more information about the product and its features.