Apache Module SSL

Module mod_ssl
This module provides SSL v2/v3 and TLS v1 support for the Apache HTTP Server, it relies on OpenSSL to provide he cryptographic engine.

SSL/TSL
Arcording to wikipedia, TLS, a.k.a., SSL (Secure Sockets Layer), establishes a private end-
to-end connection, optionally including strong mutual authentication, using a variety of cryptosystems. Initially, a handshake phase uses three subprotocols to set up a record layer, authenticate endpoints, set parameters, as well as report errors. Then, there is an ongoing
layered record protocol that handles encryption, compression, and reassembly for the remainder of the connection. The latter is intended to be completely transparent

Open SSL
OpenSSL is an open source implementation toolkit for SSL/TSL protocols to provide a fully functionality cryptographic library


References:
1. Apache Module mod_ssl
http://httpd.apache.org/docs/2.0/mod/mod_ssl.html

2. OpenSSL
http://www.openssl.org/