During Chinese New Year, and stretching into the following week, you may notice a flurry of red envelopes being exchanged almost everywhere you go. These fancy little red envelopes, called "lai see" (利是), are packets that contain good luck money. Giving lai see to people is a big part of Chinese New Year celebrations, so you don't want to miss out on giving (or receiving!) them in the following couple of weeks.
http://geoexpat.com/articles/hong-ko...-see-etiquette