SQL stands for Structured Query Language. It is the standard computer language for accessing and manipulating databases through Database Management Systems (DBMS), such as MySQL and Oracle. In addition to standard SQL that this tutorial is about, most database systems also provide their own language extensions, for example MySQL and PL/SQL.
A DBMS is a computer program that acts as a hub between one or more databases and the programs that want to use them. SQL is the language used to communicate with that database system.
Databases provide fast and efficient access to save and load data. The data is contained in tables and each table in turn contains rows and columns. The entry in a row is called a record and it contains a field for every column.
Sams - Teach Yourself SQL in 10 Minutes