SSL stands for Secure Sockets Layer and was originally created by Netscape. It is used for providing confidentiality, authenticity and integrity by establishing an encrypted link between a server and a client. This link ensures that all data passed between the web server and browsers remain private and integral. SSLv2 and SSLv3 are the 2 versions of this protocol (SSLv1 was never publicly released). After SSLv3, SSL was renamed to TLS. Those protocols are standardized and described by RFCs.
For more details check the FAQ for this algorithm.