EXECUTE IMMEDIATE IS A DYNAMIC STATEMENT. You can use this statement for example,
DECLARE
v_stmt VARCHAR2(200);
BEGIN
v_stmt :='TRUNCATE TABLE DEPT';
EXECUTE IMMEDIATE v_stmt;
END;

It truncates the DEPT table. If I am not wrong it is just replacement of DBMS_SQL package, which we use normally for DYNAMIC SQLS.

Correct me If I am wrong.