A red envelope is usually for celebrations like weddings, birthdays, or graduations. Receiving a red pouch is a sign of good luck and to ward off evil spirits. Usually it contains money and people give them during the holidays. People usually put in even amount of money including 9 because it is a homophonous to the word long. 4 should never be given or using 4 in any of the digits because the pronunciation of 4 is similar to death.