The for loop in cursors are used to make less statements to write cursor.

if u are opening a cursor normally using the open cursor then

open cursor_name;

fetch cursor_name into variable loop

exit when cursor_name notfound ;

end loop;

close cursor

in the above statement u have to explicitly open and close the cursor and also write exit statement to end the cursor loop

if we write the same using for loop then compare the statements.

for varible in cursor_name loop

statements

end loop;

the above for loop does not need a open and close explicitly since those are involved in the for loop itself.

and also never require the loop to explicitly end using any condition since it ends the loop if there are no more rows in the memory.

A cursor FOR loop processes rows in an explicit cursor. It is a shortcut because the cursor is opened rows are fetched once for each iteration in the loop the loop exits when the last row is processed and the cursor is closed automatically. The loop itself is terminated automatically at the end of the iteration where the last row is fetched.
The record is implicitly declared.