Using undergarmets as a form of subtle communication, has been a long standing tradition in relationships. Often the style and manner in which the undergarments are displayed speaks volumes with out the person having to say one word.
You know how the evening will proceed if your female counterpart comes to bed in grandma style panties and a flannel nightgown.
When she has on the spiffy red panties....oh yeah, big guy....tonight's the night.