SQL stands for "Structured Query Language" which means, in Portuguese, Structured Query Language, a standard data management language that interacts with the main databases based on the relational model.
Some of the main systems that use SQL are: MySQL, Oracle, Firebird, Microsoft Access, PostgreSQL (open source), HSQLDB (open source and written in Java).
The SQL language emerged in 1974 and was developed in IBM laboratories as an interface for the Relational Database Management System (RDBMS) called SYSTEM R. This system was created based on a 1970 article written by Edgar F. Cod.
Other languages of the genre emerged, but SQL became the most used. The creation of a standard for SQL was accomplished in 1986 by American National Standard Institute (ANSI) and in 1987 by the International Organization for Standards (ISO).
SQL is an essentially declarative language. This means that the programmer only needs to indicate what the intended purpose is for it to be executed by the RDBMS.
Some of the main SQL commands for data manipulation are: INSERT (insert), SELECT (query), UPDATE (update), DELETE (delete). SQL also makes it possible to create relationships between tables and control access to data.