SQL Server is the main relational database management system product from Microsoft. It has been around in one form or another since the late 80s (developed in partnership with Sybase), but as a standalone Microsoft product, it's here since the early 90s. In the last 20 years, SQL Server has changed and evolved, gaining newer features and functionality along the way.
The SQL Server we know today is based on what was arguably the most significant (r)evolutionary step in its history: the release of SQL Server 2005. The changes that were introduced, allowed the versions that followed the 2005 release to take advantage of newer hardware and software improvements, such as: 64-bit memory architecture, better multi-CPU ...
