what do parenthesis mean in a pattern

[robertamiller]

i have been knitting for a while but am just starting trying to read patterns. i have some sugar 'n cream and just want to make a dishclothe. should be a piece of cake but i'm stuck.
what does it mean: K2. yo. K4. (K2tog.) twice.
i don't understand what the parenthesis indicates. i get everything else.
grateful for any help
roberta