The situation is additionally confused by the fact that the version numbers do not give a good clue to how different the protocols were. Specifically:
SSLv2 was the first widely deployed version of SSL, but as this post indicates, had a number of issues.
SSLv3 is a more or less completely new protocol
TLS 1.0 is much like SSLv3 but with some small revisions made during the IETF standardization process.
TLS 1.1 is a really minor revision to TLS 1.0 to address some issues with the way block ciphers were used.
TLS 1.2 is a moderately sized revision to TLS 1.1 to adjust to advances in cryptography, specifically adding support for newer hashes in response to weaknesses in MD5 and SHA-1 and adding support for AEAD cipher suites such as AES-GCM.
TLS 1.3 is mostly a new protocol though it reuses some pieces of TLS 1.2 and before.
Each of these protocols has been designed so that you could automatically negotiate versions, thus allowing for clients and servers to independently upgrade without loss of connectivity.
SSLv2 was the first widely deployed version of SSL, but as this post indicates, had a number of issues.
SSLv3 is a more or less completely new protocol
TLS 1.0 is much like SSLv3 but with some small revisions made during the IETF standardization process.
TLS 1.1 is a really minor revision to TLS 1.0 to address some issues with the way block ciphers were used.
TLS 1.2 is a moderately sized revision to TLS 1.1 to adjust to advances in cryptography, specifically adding support for newer hashes in response to weaknesses in MD5 and SHA-1 and adding support for AEAD cipher suites such as AES-GCM.
TLS 1.3 is mostly a new protocol though it reuses some pieces of TLS 1.2 and before.
Each of these protocols has been designed so that you could automatically negotiate versions, thus allowing for clients and servers to independently upgrade without loss of connectivity.