According to me, An Implicit cursor is a temporary work area that created by default when DML statements like, INSERT, UPDATE, and DELETE statements are executed. They are also created when a SELECT statement that returns just one row is executed.
The interesting thing is that the implicit cursor is not only faster, but it is actually doing more work, since it includes a NO_DATA_FOUND and a TOO_MANY_ROWS exception check.
When a Query is executing, an implicit cursor automatically created. like
-- Time implicit cursor.
l_start := DBMS_UTILITY.get_time;
FOR i IN 1 .. l_loops LOOP
DBMS_OUTPUT.put_line('Implicit: ' || (DBMS_UTILITY.get_time - l_start));