I have a surge protector with 8 slots (1 side = 5, 3 on the other) the 3 on the right side say "transformer" .?

what is 'transformer' mean? and what should I be plugging into it (as a precaution) .. I want to know what is most appropriate. I have: 2 external HD's, 1 printer/scanner, 1 external CD burner, 1 casio CD printer, cable modem .. and of course power cords for my moniter and PC ... so which ones should or shouldn't be used in the transformer slots? Thanks for your answers