Hyper Text Transfer Protocol Secure (HTTPS) is the method of communicating between servers and browsers, it uses SSL/TLS.
Secure Sockets Layer (SSL) and its successor Transport Layer Security (TLS) are often both referred to as SSL.
TLS is the industry standard method of securing communications between servers and browsers. It encrypts the communications with a Certificate which is validated by a Certificate Authority. As long as the Certificate and Certificate Authority are verified the transmissions between the server and browser are secure and can not be stolen or changed.
More: Symantec / Wikipedia / GlobalSign / Digicert / SSL.com
Since 1995, when SSL was first introduced, there have been several versions, each stronger than the prior version. The current version, TLS 1.2 is supported by most newer browsers, there is a version 1.3, but its not yet supported by any browsers. It is important to be sure that a web site is using the latest version available of SSL/TLS, because prior versions have been broken by hackers.
3rdKey.com uses HTTPS over TLS 1.2 because its the accepted method of ensuring secure communication between server and browser. According to Symantec, "It uses encryption algorithms to scramble data in transit, preventing hackers from reading it as it is sent over the connection." --Symantec
