SQL is a database language for working on databases
SQL is an abbreviation for structured query language, and is a database language for creating database structures in relational database and for working on and querying the database based on it. This means that SQL lets you select, enter, update and again delete data from a database. In addition, it lets you create, modify and again delete SQL database tables. SQL is generally easy for developers to learn. The more the complex the database requests, the more complex the SQL queries which are the queries to the database.
SQL has become the standard
SQL was developed by IBM in the 1970s and is now a standard of the American National Standards Institute (Ansi). The “language range” of SQL is huge, and this is one of the reasons why this standard faces hardly any competition. SQL queries are passed as a string of a function of PHP, which is then forwarded to the database and can be run. SQL as a database language is based on relational algebra, its syntax is simple and its word choice is modelled on the English language. The word ‘query’ is contained in the name SQL. With queries, the data is retrieved from the database and provided to the user with application software.
You can find more information on SQL on Wikipedia: https://en.wikipedia.org/wiki/SQL