TLS (Transport Layer Security) is used to secure connections on the Web. TLS is essential to the Web, providing the ability to form connections that are confidential, authenticated, and tamper-proof. This has made it a big focus of security research, and over the years, a number of bugs that had significant security implications have been found in the protocol. Revisions have been published to address these flaws.
The original TLS 1.0, heavily based on Netscape's SSL 3.0, was first published in January 1999. TLS 1.1 arrived in 2006, while TLS 1.2, in 2008, added new capabilities and fixed these security flaws. Irreparable security flaws in SSL 3.0 saw support for that protocol come to an end in 2014; the browser vendors now want to make a similar change for TLS 1.0 and 1.1.