PL/SQL blocks are made up of PL/SQL and SQL statements. A block is a functional unit made up of an optional declaration section, an execution section, and an optional exception or error handling section. A block has the following syntax

DECLARE
   variable declaration
BEGIN
   Program Execution
EXCEPTION
   Exception handling
END;

Declare section is used to declare variables, constants, records, and cursors used in the execution section.
Execution section starts with BEGIN and ends with END. Program logic is written in this section.
Exception section contains code for error handling