PL/SQL

procedural constructs + SQL statements ---> PL/SQL
PL SQL PLSQL

plsql is prpetiory lanuguage of oracle
It has seemless integration of procedural constructs like variables,if,while,for data structure.

pl/sql compiler or pl/sql engine
takes whole block as pl/sql and separates the sql and pl part,procedural staatement executer executes pl
sql statemnt executer will execute sql than again gets integrated

pl/sql engine can be on client side or whole thing can exists in database itself

features
Ability to real life programming
Tight inter-relation with SQL
Full portability
Access to predefined packages eg dbms_lob,utl_http
Tight security(same securt as database othr users)
Better performance(5-sql sataments takes more time than one plsql block)
APEX oracle app express-web application development using ajax or others