A TLS connection runs a handshake (negotiate version, cipher suite and key-exchange group, exchange key shares, authenticate with certificates and signatures, derive keys) and then the record protocol, which encrypts application data with an AEAD. TLS 1.3 is now specified in RFC 9846 (July 2026), which obsoletes RFC 8446 as well as RFC 5246 (TLS 1.2) and adds requirements for TLS 1.2 implementations; TLS 1.0 and 1.1 were deprecated by RFC 8996 (2021).
History: SSL 2.0 (1995) and 3.0 (1996) came from Netscape; TLS 1.0 (1999), 1.1 (2006), 1.2 (2008) and 1.3 (2018) followed. Each generation removed broken constructions, ending in TLS 1.3 with forward-secret key exchange only, AEAD-only cipher suites and an encrypted handshake.
Variants: DTLS for datagrams (DTLS 1.3, RFC 9147), QUIC (which embeds the TLS 1.3 handshake) and mTLS when clients present certificates. The post-quantum transition happens in the key exchange (hybrid groups such as X25519MLKEM768) and, later, in certificates. "SSL" survives only as a name: SSL certificates, OpenSSL, ssl_ configuration directives.