plsql inner blocks

DECLARE
SUBTYPE name IS char(20);
SUBTYPE message IS varchar2(100);
today date:=sysdate;
salutation name;
greetings message;
counter binary_integer := 0;
greetings1 varchar2(20) DEFAULT 'Have a Good Day';

BEGIN
salutation := 'Reader ';
greetings := 'Welcome to my  Blog';

 dbms_output.put_line('Hello ' || salutation || greetings||today);
 dbms_output.put_line('Hello ' ||'Counter :'||counter||'  '||'Greet:'||greetings1);
END;
/