The term 'SSL certificate' has persisted, and will likely persist for the foreseable future, because given the choice of saying 'SSL' or 'X.509' the former tends to roll off the tongue more comfortably.
Doubtless a linguistic expert could wax lyrical over the S sound versus the X sound.
When a secure connection is initially established it will, depending on the implementation, negotiate support of the particular protocol from the set SSLv3, TLSv1, TLSv1.1 or TLSv1.2.
Such is the pervasive power of the name SSL that in most cases what is called SSL is most likely using TLS - for instance Open SSL supports both SSL (v3) and TLS (TLSv1, TLSv1.1 and TLSv1.2) protocols.
In the case of HTTPS the well-known port number is 443, in the case of IMAPS - port 993, POP3S - port 995 etc..
The next level of description requires some familiarity with the terms MAC (Message Authentication Code), Secure hashes, symmetric and asymmetric cryptographic algorithms.
Bad news: If you self-sign your certificates nobody but you and your close family (perhaps) may trust them.
The term SSL certificate became common due to the adoption of the X.509 (one of the ITU X.500 Directory standards) certificate format by Netscape when it designed the original versions of the SSL (Secure Socket Layer) protocol, eons ago, when the world was still young, dinosuars still roamed, and the Internet was a friendly place.
For we, mere mortals, its chief merit may be that it's shorter (3 versus 4 syllables).
The current guide includes SSL, TLS, some detail about X.509 and its usage as well as some explanation about certificate types, including EV certificates, and the trust process.
The RFC may also be viewed at XXXX/ which also contains various RFC status information (including errata) together with a list of alternative formats, such as, text, PDF and HTML (this is the working area version of the document). We update the page from time-to-time when we can think of nothing better to do with our lives and now keep a change log in case you ever happen to read it twice. Secure Sockets Layer (SSL) is a Netscape protocol originally created in 1992 to exchange information securely between a web server and a browser where the underlying network was insecure.
It went through various iterations and is now at version 3 (dating from 1995) and used in a variety of clientserver applications.