Microsoft's SQL Server is a suite of relational database management system (RDBMS) products providing multi-user database access functionality. It originated from the Sybase SQL Server 4.x codebase and Transact-SQL dialect (t-sql), but it has forked significantly since then.
SQL Server is available in multiple versions (typically identified by release year), each of which are subdivided into editions to distinguish between product functionality. The latest released version is SQL Server 2019 which was released on November 4th, 2019.