TLS is the modern successor to SSL. SSL (notably SSL 2.0 and SSL 3.0) was an early protocol family for securing network communications, providing encryption, integrity, and endpoint authentication for applications like HTTPS. Over time, weaknesses were discovered in SSL's design and in the cryptographic mechanisms commonly used with it. TLS was introduced as an improved, standardized evolution (starting with TLS 1.0, based on SSL 3.0 but with important fixes), and later versions (TLS 1.2 and TLS 1.3) significantly strengthened security by removing weak ciphers, improving key exchange, and tightening handshake and record protections. In practice, when people say ''SSL'' today, they often mean ''TLS,'' but true SSL is deprecated and should not be used. SSL is not a replacement of TLS, and the two are not identical in security---TLS versions incorporate substantial improvements and modern cryptographic best practices. SSL is also not limited to email; it was widely used for web traffic and other protocols. Therefore, the correct relationship is that TLS replaced SSL to provide improved security.