SQL> create procedure foo
  2  is
  3  begin
  4    dbms_output.put_line('foo has been executed');
  5  end;
  6  /

Procedure created.

SQL> set serverout on
SQL> execute foo
foo has been executed

PL/SQL procedure successfully completed.

SQL> begin
  2    foo;
  3  end;
  4  /
foo has been executed

PL/SQL procedure successfully completed.