SQL*Plus provides basic command-line interface to Oracle instances. Programmers and DBAs commonly use it as the default available fundamental interface in almost any Oracle software installation, which includes running SQL and PL/SQL commands interactively or from a script.
Commands run from sqlplus fall under three(3) categories:
- SQL Statements
- PL/SQL Blocks
- SQL*Plus internal commands
For more information see the 11g SQL*Plus User's Guide and Reference (pdf).