2.) PL/SQL can be the application language just like Java or PHP can. PL/SQL might be the language we use to build, format and display those screens, web pages and reports.SQL may be the source of data for our screens, web pages and reports.
3.) SQL is executed one statement at a time. PL/SQL is executed as a block of code.
4.) SQL tells the database what to do (declarative), not how to do it. In contrast, PL/SQL tell the database how to do things (procedural).
5.) SQL is used to code queries, DML and DDL statements. PL/SQL is used to code program blocks, triggers, functions, procedures and packages.
6.) We can embed SQL in a PL/SQL program, but we cannot embed PL/SQL within a SQL statement.
7.) SQL is a language that is used by relational database technologies such as Oracle, Microsoft Access, and Sybase etc., PL/SQL is commonly used to write data-centric programs to manipulate data in an Oracle database. PL/SQL language includes object oriented programming techniques such as encapsulation, function overloading, and information hiding (all but inheritance).