SQL stands for 'Structured Query Language' which is an ANSI standard for relational database management systems (RDBMS).
We often integrate these databases into clients' website applications where large amounts of persistent data are required.
We use two main implementations of this language.
SQL Server is a very powerful database server running on Microsoft operating systems.
We use it for C# projects needing industrial strength database operations running on a Microsoft server with MS Internet Information Server (IIS).
It is also possible to install SQL Server on Linux and MacOS.
We have used this open source database extensively, mostly with PHP coding on Linux servers.
MySql is installed on our cloud server which is Linux based.