The language developed by IBM to manipulate the data stored within Codd's model was originally called Structured English Query Language (SEQUEL) with the word English later being dropped in favor Structured Query Language (SQL).
SQL is a language that provides an interface to relational database systems. Structured Query Language or SQL is a standard Database language which is used to create, maintain and retrieve the relational database. It is particularly used to work with structured data where there is relations associated within the data itself.
SQL encompasses DML (Data Manipulation Language), for INSERTs, UPDATEs, DELETEs and DDL (Data Definition Language), used for creating and modifying tables and other database structures.